Field of the Invention
[0001] The present invention relates to a hydraulic ram for an excavator coupler for coupling
an attachment, such as an excavating bucket, to the arm of an excavator.
Background to the Invention
[0002] It is well known for an excavator coupler to have at least one hydraulically operated
latching hook for engaging with a rear pin of an attachment, e.g. a bucket, to secure
the attachment to the arm of an excavator, the latching hook being movable into and
out of a latching state under the action of a hydraulic ram. A major problem with
existing couplers is that operator misuse or incorrect operation of the coupler can
cause the attachment to swing or even completely detach from the coupler posing a
safety hazard. When an operator uses a coupler to lift an attachment he cannot always
determine that the latching hook has engaged with the rear pin of the attachment correctly.
This can lead to the attachment swinging on a single pin with danger to personnel
and possible damage to plant and equipment.
Summary of the Invention
[0003] Accordingly, a first aspect of the present invention provides a hydraulic ram for
an excavator coupler comprising a cylinder having a head end adapted to be connected
to one of the body of the excavator coupler and a latching hook thereof, a piston
slidably mounted in the cylinder between a retracted position adjacent the head end
of the cylinder and an extended position adjacent a distal end of the cylinder, opposite
said head end, said piston dividing the cylinder into a first working chamber adjacent
said head end of the cylinder and a second working chamber adjacent said distal end
of the cylinder, a piston rod extending from the piston through said second working
chamber of the cylinder to extend out of the distal end of the cylinder, a distal
end of the piston rod being adapted to be connected to the other of the body of the
excavator coupler and said latching hook thereof, a first fluid supply port being
provided for supplying pressurised fluid into said first working chamber to urge the
piston and piston rod away from said head end of the cylinder towards said extended
position, wherein a signal port is provided in the side wall of the cylinder, said
signal port being arranged to communicate with said first working chamber when the
piston is in its extended position.
[0004] Preferably said signal port is arranged to be obscured by said piston, preventing
communication between said signal port and the first working chamber of the cylinder,
when the piston is in a partly extended position.
[0005] In use, the length of the ram is selected such that the piston is in said partly
extended position when a latching hook of an excavator coupler to which the ram is
fitted is in engagement with a rear pin of an attachment, such that the signal port
is isolated from the first working chamber of the cylinder, preferably by being obscured
by the piston, when the latching hook is engaged with the rear pin of an attachment.
Should the latching hook fail to engage the rear pin of the attachment, the piston
is able to move to its fully extended position, exposing the signal port whereby pressurised
fluid from the first working chamber passes into said signal port. The flow of fluid
into said signal port can be detected by suitable sensing means, such as a pressure
or flow sensor, for example by detecting a pressure drop in said first working chamber,
providing an indication that the latching hook is not in correct engagement with the
rear pin of the attachment.
[0006] Said hydraulic ram may comprise a double acting ram, a second fluid supply port being
provided for supplying pressurised fluid into said second working chamber of the cylinder
for moving the piston towards its retracted position. Said signal port may be arranged
to communicate with a fluid line communicating with said second fluid supply port.
A check valve may be associated with said signal port preventing the passage of pressurised
fluid from said fluid line to said signal port.
[0007] According to a second aspect of the present invention there is provided a coupler
for an excavator, the coupler comprising a body having a spaced-apart recesses for
receiving respective attachment pins of an excavator attachment; a latching member
being associated with at least one of said recesses, said latching member being movable
into and out of a latching state in which it is capable of retaining one of said attachment
pins of said excavator attachment in said recess; a hydraulic ram being provided for
moving said latching member into said latching state; said hydraulic ram comprising
a cylinder having a head end connected, either directly or indirectly, to one of the
body of the coupler and the latching member, a piston slidably mounted in the cylinder
between a retracted position adjacent the head end of the cylinder and an extended
position adjacent a distal end of the cylinder, opposite said head end, said piston
dividing the cylinder into a first working chamber adjacent said head end of the cylinder
and a second working chamber adjacent said distal end of the cylinder, a piston rod
extending from the piston through said second working chamber of the cylinder to extend
out of the distal end of the cylinder, a distal end of the piston rod being connected,
either directly or indirectly, to the other of the body of the coupler and said latching
member, a first fluid port being provided for supplying pressurised fluid from a first
fluid line into said first working chamber to move the piston and piston rod away
from said head end of the cylinder towards said extended position adjacent the distal
end of the cylinder to move said latching member into its latching state, the length
of said ram being selected such that the piston is in a partly extended position,
spaced from said distal end of the cylinder, when the latching member is in engagement
with said attachment pin, thereby applying a biasing force against the attachment
pin when the latching member is in its latched state, wherein a signal port is provided
in a side wall of the cylinder, said signal port being isolated from the first working
chamber of the cylinder when the piston is in said partly extended position when said
latching hook is in engagement with said attachment pin, said signal port being placed
in communication with said first working chamber when the piston moves to its fully
extended position, for example if the attachment pin is not positioned in said recess
in the coupler when the latching member is moved towards its latching state, thereby
providing an indication that the latching member is not in correct engagement with
the attachment pin.
[0008] The flow of oil through the signal port may be detected by any suitable means, such
as a pressure sensor of flow meter.
[0009] The spaced-apart recesses of the coupler may comprise a front recess adapted to receive
a front pin of an attachment, and a rear recess, adapted to receive a rear pin of
an attachment, said latch member being associated with said rear recess such that
the latching member engages the rear pin of the attachment when the latching member
is in its latched state and the rear pin is located in the rear recess.
[0010] Preferably said front recess comprises an opening facing away from said rear recess
such that said front pin is retained within said front recess when the rear pin is
engaged within said rear recess.
[0011] Preferably said signal port is arranged to be obscured by said piston, preventing
communication between said signal port and the first working chamber of the cylinder,
when the piston is said partly extended position.
[0012] Preferably the hydraulic ram comprises a double acting ram, a second fluid port being
provided for supplying pressurised fluid from a second fluid line into said second
working chamber of the cylinder for moving the piston towards its retracted position
to move the latching member out of its latching state. Said signal port may be arranged
to communicate with said second fluid port. A check valve may be associated with said
signal port preventing the passage of pressurised from said second fluid port to said
signal port while permitting fluid to flow from said signal port to said second fluid
port.
[0013] Further advantageous aspects of the invention will be apparent to a skilled person
upon review of the following description of a preferred embodiment and with reference
to the accompanying drawings.
Brief Description of the Drawings
[0014] An embodiment of the invention is now described by way of example and with reference
to the accompanying drawings in which:
Figure 1 is a side view of a coupler for an excavator in accordance with an embodiment
of the present invention;
Figure 2 is a side view of the coupler of Figure 1 showing the position of the latching
hook when it has failed to engage the rear pin of the attachment;
Figure 3 is a side view of the coupler of Figure 1 showing the position of the latching
hook when engaging a rear pin of an attachment having closely spaced pins;
Figure 4 is side sectional view of the hydraulic ram of the coupler of Figure 1;
Figure 5 is a side sectional view of the hydraulic ram of the coupler of Figure 1
when the coupler is in the configuration shown in Figure 2; and
Figure 6 is a side sectional view of the hydraulic ram of the coupler of Figure 1
when the coupler is in the configuration shown in Figure 3.
Detailed Description of the Drawings
[0015] This invention relates to an improved hydraulic coupler employing a modified hydraulic
ram within the coupler which provides an indication when the piston rod of the ram
is fully out-stroked (fully extended). This fully out-stroked condition can only occur
when a latching hook of the coupler has missed the rear pin of the attachment so the
indication can be used to warn the operator that the rear pin is not engaged. Because
of the environment in which the coupler works wires to the coupler and electrical
and electronic sensors within the coupler can prove unreliable and troublesome. However
hydraulic oil is fed to the hydraulic ram of the coupler via hydraulic hoses. The
ram is designed so that it will pass a limited amount of oil continuously at full
stroke and this can be detected remotely from the coupler.
[0016] As shown in Figures 1 to 3, a coupler for attaching an attachment, such as a bucket,
to an arm of an excavator comprises a body 2 having a front recess 4 for receiving
a front pin 6 of an attachment (not shown) and a rear recess 8 for receiving a rear
pin 10 of the attachment. A latching hook 12 is pivotally mounted on the body 2 to
be moveable into and out of a latching state, wherein the latching hook 12 engages
the rear pin 10 of the attachment to retain the pin 10 in the rear recess 8. In an
alternative embodiment the latching hook 12 may be linearly slidable or otherwise
displaceable into and out of its latching state.
[0017] The latching hook 12 is moveable into and out of its latching state by means of a
double acting hydraulic ram 14. The ram 14 comprises a cylinder 16 having a closed
head end 18 mounted on the body 2 of the coupler. A piston 20 is slidably mounted
within the cylinder along the longitudinal axis of the cylinder 16 between a retracted
position, adjacent the head end 18 of the cylinder 16, and an extended position adjacent
a distal end 22 of the cylinder, opposite said head end 18.
[0018] The piston 20 divides the cylinder 16 into first and second working chambers 24,26.
A piston rod 28 extends from the piston 20 through the second working chamber 26 and
out of the distal end 22 of the cylinder 16, a distal end of the piston rod 28 being
connected to the latching hook 12.
[0019] As is conventional in the art, the hydraulic ram 14 is fed with pressurised hydraulic
fluid from either the excavator main hydraulic line or the excavator servo (reduced
pressure) hydraulic line. From a valve mounted normally within the engine/hydraulic
compartment of the machine two high pressure hydraulic pipes either flexible or a
mixture of flexible and rigid run from the engine compartment, up the excavator boom,
unsupported across the excavator boom to dipper connection, down the dipper arm, unsupported
across the excavator dipper to hitch, and terminate at the hydraulic ram 14 within
the coupler body 2. The first and second working chambers 24,26 of the ram 14 are
selectively fed with pressurised hydraulic fluid to selectively extend and retract
the piston rod 28.
[0020] A first fluid line communicates with the first working chamber 24 via a first fluid
port A in the side wall of the cylinder adjacent the head end thereof to supply pressurised
fluid to the first working chamber 24 to move the piston 20 towards its extended position,
extending the piston rod 28 from the cylinder 16 and moving the latching hook 12 towards
into its latched state.
[0021] A second fluid line communicates with the second working chamber 26 via a second
fluid port B in the wall of the cylinder 16 adjacent the distal end 22 thereof to
supply pressurised fluid to the second working chamber 26 to move the piston 20 towards
its retracted position, retracting the piston rod 28 into the cylinder 16 and moving
the latching hook 12 out of its latched state.
[0022] A signal line communicates with a signal port
Bs provided in the wall of the cylinder 16 adjacent the second fluid port
B, spaced from the distal end of the cylinder 16. The signal line feeds into the second
fluid line, thus the signal port
Bs is in fluid communication with the second fluid port
B.
[0023] The signal port
Bs is position in the wall of the cylinder 16 to be uncovered by the piston 20 when
the piston 20 is caused to travel past the signal port position to a fully extended
or out-stroked position by the application of pressure to the first working chamber
24 via the first fluid port
A. The uncovering of the signal port
Bs will allow fluid from the high pressure side of the piston (i.e. the first working
chamber 24) to enter the signal port
Bs. This will cause fluid to circulate from the first fluid line to the second fluid
line when the piston 20 moves past the signal port
Bs as the piston reaches is fully extended position. This circulation of oil can then
be detected and used as an indication of excessive piston travel.
[0024] The signal port
Bs and/or its associated fluid line has a much smaller diameter than either of the first
or second ports A, B and associated first and second fluid lines, limiting the amount
of oil that it can pass. Because the amount of oil escaping is small compared to the
volume of oil supplied to the cylinder, the escape of oil will have little influence
on the overall action of the ram 14.
[0025] In use, the front pin 6 of an attachment is manoeuvred into the front recess 4 of
the coupler. The coupler is then manipulated to swing the rear pin 10 into the rear
recess 8. Pressurised fluid is supplied to the first port
A of the cylinder 16 and enters the first working chamber 24 of the cylinder 16. This
causes the piston 20 to move to the right (as illustrated in Figures 4 to 6) and the
piston rod 28 to be extended from the cylinder 16, moving the latching hook 12 towards
its latching state. Fluid from the second working chamber 26 of the cylinder 16 will
leave the cylinder via ports
Bs and
B.
[0026] If the latching hook 12 correctly engages the rear pin 10 of the attachment, the
piston 20 is arrested in a partly extended position, as illustrated in Figures 1 and
4. In such position, the piston 20 obscures the signal port
Bs, isolating the signal port
Bs from the first working chamber of the cylinder 16.
[0027] Figures 2 and 5 illustrate the situation should the latching hook 12 failed to correctly
engage the rear pin 10 of the attachment. As can be seen from Figure 2, if the latching
hook 12 is moved to its latching state when the rear pin 10 is not correctly located
in the rear recess 8, the latching hook 12 fails to engage the rear pin 10 and the
piston 20 of the ram 14 is able to move to its fully extended position adjacent the
distal end 22 of the cylinder 16, fully extending the piston rod 28. Because the piston
20 has moved to the extreme right hand distal end of the cylinder 16, the piston 20
has uncovered signal port
Bs such that the signal port
Bs communicates with the first working chamber 24 of the cylinder 26. This means fluid
entering the first working chamber 24 of the cylinder 16 through port
A will also be able to drain through port Bs as indicated by arrow X and into the second
fluid line.
[0028] The flow of fluid through the signal port
Bs can be detected by suitable means, such as a pressure sensor or flow sensor, to provide
an indication to the operator that the attachment is not correctly coupled to the
arm.
[0029] In the preferred embodiment the size of the signal port
Bs and its associated signal line is substantially smaller than the size of the second
port
B and the second fluid line. This means that, when the supply of oil to the cylinder
is reversed (high pressure oil supplied to the second working chamber 26 of the cylinder
16) with the piston 20 in its fully extended position, a greater volume of fluid will
enter the second working chamber 26 of the cylinder 16 through the second port B than
that entering the first working chamber 24 through the signal port
Bs, causing the piston 20 to move to the left, closing off communication between the
signal port
Bs and the first working chamber 24.
[0030] Figures 3 and 6 illustrate the situation wherein the coupler is attached to an attachment
having a reduced pin spacing. In such situation the latching hook 12 engages the rear
pin 10 of the attachment earlier, such that the extension of the piston rod 28 from
the cylinder 16 is less before the latching hook 12, and thus further extension of
the ram, is arrested by engagement of the latching hook 12 with the rear pin 10 of
the attachment.
[0031] In an alternative embodiment, the signal port
Bs may be provided with a non return valve, whereby fluid entering the first working
chamber 24 of the cylinder 14 through the first port
A will still be able to leave the first working chamber 24 of the cylinder 16 through
port
Bs when the piston 20 is in its fully extended position. However when oil is supplied
to the second port B to retract the cylinder, the non-return valve associated with
the signal port Bs prevents oil flowing into the first working chamber 24 of the cylinder
16 through the signal port
Bs. The non-return valve may be required in instances where there is insufficient flow
of oil from the pump to overcome the leakage through
Bs and cause the piston 20 to retract. This circulation of hydraulic fluid from the
first port A of the cylinder through the signal port Bs which occurs at full extension
of the piston rod (or any position along the length of the cylinder dependant upon
the position of the signal port
Bs) may be used to operate a switch mounted remotely from the coupler (e.g. a flow switch
or a pressure switch), to provide a signal indicating that the extension of the cylinder
has exceeded the preset value.
[0032] This preset value may be slightly greater than the engagement position of the coupler
rear hook with the maximum expected pin spread of the range of attachments. This signal
can then be used to operate an indicator, which could be visual, audible or both,
alerting the operator to incorrect locking of the attachment.
[0033] Whilst the hydraulic ram in accordance with the present invention has been described
in relation to use in a hydraulic coupler for an excavator to detect and alert an
operator to a situation wherein an attachment is incorrectly coupled to an arm of
an excavator, it is envisaged that the hydraulic ram may be used in other applications
wherein it is desirable to detect a fully out-stroked or fully extended state of the
ram.
[0034] The invention is not limited to the embodiment(s) described herein but can be amended
or modified without departing from the scope of the present invention.
1. A hydraulic ram for an excavator coupler comprising a cylinder (16) having a head
end (18) adapted to be connected to one of the body (2) of the excavator coupler and
a latching hook (12) thereof, a piston (20) slidably mounted in the cylinder (16)
between a retracted position adjacent the head end (18) of the cylinder (16) and an
extended position adjacent a distal end (22) of the cylinder (16), opposite said head
end (18), said piston (20) dividing the cylinder (16) into a first working chamber
(24) adjacent said head end (18) of the cylinder (16) and a second working chamber
(26) adjacent said distal end (22) of the cylinder (16), a piston rod (28) extending
from the piston (20) through said second working chamber (26) of the cylinder (16)
to extend out of the distal end (22) of the cylinder (16), a distal end of the piston
rod (28) being adapted to be connected to the other of the body (2) of the excavator
coupler and said latching hook (12) thereof, a first fluid supply port (A) being provided
for supplying pressurised fluid into said first working chamber (24) to urge the piston
(20) and piston rod (28) away from said head end (18) of the cylinder (16) towards
said extended position, wherein a signal port (Bs) is provided in the side wall of
the cylinder (16), said signal port (Bs) being arranged to communicate with said first
working chamber (24) when the piston (20) is in its extended position.
2. A hydraulic ram as claimed in claim 1, wherein said signal port (Bs) is arranged to
be obscured by said piston (20), preventing communication between said signal port
(Bs) and the first working chamber (24) of the cylinder (16), when the piston (20)
is in a partly extended position.
3. A hydraulic ram as claimed in claim 1 or claim 2, wherein, in use, the length of the
ram (14) is selected such that the piston (20) is in said partly extended position
when a latching hook (12) of an excavator coupler to which the ram is fitted is in
engagement with a rear pin (10) of an attachment, such that the signal port (Bs) is
isolated from the first working chamber (24) of the cylinder (16) when the latching
hook (12) is engaged with the rear pin (10) of an attachment.
4. A hydraulic ram as claimed in any preceding claim, wherein said hydraulic ram (14)
comprises a double acting ram, a second fluid supply port (B) being provided for supplying
pressurised fluid into said second working chamber (26) of the cylinder (16) for moving
the piston (20) towards its retracted position, wherein said signal port (Bs) is arranged
to communicate with a fluid line communicating with said second fluid supply port
(B).
5. A hydraulic ram as claimed in claim 4, wherein a check valve is associated with said
signal port (Bs) preventing the passage of pressurised fluid from said fluid line
to said signal port (Bs).
6. A coupler for an excavator, the coupler comprising a body (2) having a spaced-apart
recesses (4,8) for receiving respective attachment pins (6,10) of an excavator attachment;
a latching member (12) being associated with at least one of said recesses (4,8),
said latching member (12) being movable into and out of a latching state in which
it is capable of retaining one of said attachment pins (6,10) of said excavator attachment
in the respective recess (4,8); a hydraulic ram (14) being provided for moving said
latching member (12) into said latching state; said hydraulic ram (14) comprising
a cylinder (16) having a head end (18) connected, either directly or indirectly, to
one of the body (2) of the coupler and the latching member (12), a piston (20) slidably
mounted in the cylinder (16) between a retracted position adjacent the head end (18)
of the cylinder (16) and an extended position adjacent a distal end (22) of the cylinder
(16), opposite said head end (18), said piston (20) dividing the cylinder (16) into
a first working chamber (24) adjacent said head end (18) of the cylinder (16) and
a second working chamber (26) adjacent said distal end (22) of the cylinder (16),
a piston rod (28) extending from the piston (20) through said second working chamber
(26) of the cylinder (16) to extend out of the distal end (22) of the cylinder (16),
a distal end of the piston rod (28) being connected, either directly or indirectly,
to the other of the body (2) of the coupler and said latching member (12), a first
fluid port (A) being provided for supplying pressurised fluid from a first fluid line
into said first working chamber (24) to move the piston (20) and piston rod (28) away
from said head end (18) of the cylinder (16) towards said extended position adjacent
the distal end (22) of the cylinder (16) to move said latching member (12) into its
latching state, the length of said ram (14) being selected such that the piston (20)
is in a partly extended position, spaced from said distal end (22) of the cylinder
(16), when the latching member (12) is in engagement with said attachment pin (10),
thereby applying a biasing force against the attachment pin (10) when the latching
member (12) is in its latched state, wherein a signal port (Bs) is provided in a side
wall of the cylinder (16), said signal port (Bs) being isolated from the first working
chamber (24) of the cylinder (16) when the piston (20) is in said partly extended
position when said latching member (12) is in engagement with said attachment pin
(10), said signal port (Bs) being placed in communication with said first working
chamber (24) when the piston (20) moves to its fully extended position, for example
if the attachment pin (10) is not positioned in said recess (8) in the coupler when
the latching member (12) is moved towards its latching state, thereby providing an
indication that the latching member (12) is not in correct engagement with the attachment
pin (10).
7. A coupler as claimed in claim 6, wherein the spaced-apart recesses (4,8) of the coupler
comprise a front recess (4) adapted to receive a front pin (6) of an attachment, and
a rear recess (8), adapted to receive a rear pin (10) of an attachment, said latch
member (12) being associated with said rear recess (8) such that the latching member
(12) engages the rear pin (10) of the attachment when the latching member (12) is
in its latched state and the rear pin (10 is located in the rear recess (8).
8. A coupler as claimed in claim 7, wherein said front recess (4) comprises an opening
facing away from said rear recess (8) such that said front pin (6) is retained within
said front recess (4) when the rear pin (10) is engaged within said rear recess (8).
9. A coupler as claimed in any of claims 6 to 8, wherein said signal port (Bs) is arranged
to be obscured by said piston (20), preventing communication between said signal port
(Bs) and the first working chamber (24) of the cylinder (16), when the piston (20)
is said partly extended position.
10. A coupler as claimed in any of claims 6 to 9, wherein the hydraulic ram (14) comprises
a double acting ram, a second fluid port (B) being provided for supplying pressurised
fluid from a second fluid line into said second working chamber (26) of the cylinder
(16) for moving the piston (20) towards its retracted position to move the latching
member (12) out of its latching state, wherein said signal port (Bs) is arranged to
communicate with a fluid line communicating with said second fluid supply port (B).
11. A coupler as claimed in claim 10, wherein a check valve is associated with said signal
port (Bs) preventing the passage of pressurised from said second fluid port (B) to
said signal port (Bs) while permitting fluid to flow from said signal port (Bs) to
said second fluid port (B).