U.S. patent application number 14/158226 was filed with the patent office on 2014-05-15 for hydraulic system thermal contraction compensation apparatus and method.
This patent application is currently assigned to Manitowoc Crane Companies, LLC. The applicant listed for this patent is Manitowoc Crane Companies, LLC. Invention is credited to Timothy F. Elliott, Stephen D. Smith.
Application Number | 20140130660 14/158226 |
Document ID | / |
Family ID | 42115774 |
Filed Date | 2014-05-15 |
United States Patent
Application |
20140130660 |
Kind Code |
A1 |
Elliott; Timothy F. ; et
al. |
May 15, 2014 |
HYDRAULIC SYSTEM THERMAL CONTRACTION COMPENSATION APPARATUS AND
METHOD
Abstract
An apparatus for compensating for fluid contraction in a
hydraulic powered telescoping boom may include a monitor
determining the elevation angle of the telescoping boom, a supply
of hydraulic fluid, and a fluid control responsive to the monitor.
The fluid control provides the hydraulic fluid from the supply to a
hydraulic cylinder controlling extension of the telescoping boom
when the elevation angle exceeds a predetermined threshold angle to
compensate for thermal contraction of hydraulic fluid and thus
prevent uncommanded boom retraction. A method in accordance with
the invention is also disclosed.
Inventors: |
Elliott; Timothy F.;
(Chambersburg, PA) ; Smith; Stephen D.;
(Mercersburg, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Manitowoc Crane Companies, LLC |
Manitowoc |
WI |
US |
|
|
Assignee: |
Manitowoc Crane Companies,
LLC
Manitowoc
WI
|
Family ID: |
42115774 |
Appl. No.: |
14/158226 |
Filed: |
January 17, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12559253 |
Sep 14, 2009 |
8631651 |
|
|
14158226 |
|
|
|
|
61202030 |
Jan 21, 2009 |
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Current U.S.
Class: |
91/392 ;
91/471 |
Current CPC
Class: |
B66C 23/62 20130101;
B66C 23/705 20130101; B66C 13/20 20130101; B66C 23/88 20130101 |
Class at
Publication: |
91/392 ;
91/471 |
International
Class: |
B66C 13/20 20060101
B66C013/20 |
Claims
1. An apparatus for compensating for fluid contraction in a
hydraulic powered telescoping boom, comprising: a monitor
determining an elevation angle of the telescoping boom; a supply of
hydraulic fluid; and a fluid control responsive to the monitor for
providing hydraulic fluid from the supply to a hydraulic device
controlling extension of the telescoping boom when the elevation
angle exceeds a predetermined threshold angle.
2. The apparatus according to claim 1, wherein the fluid control
comprises: a control valve configured to supply hydraulic fluid to
the hydraulic device in response to a signal generated by the
monitor when the elevation angle of the boom exceeds the threshold
angle.
3. The apparatus according to claim 1, wherein the monitor
determines when the angle of elevation of the boom is at least
thirty-five degrees elevation above horizontal.
4. The apparatus according to claim 1, further comprising: a
pressure sensor monitoring pressure of the fluid provided to the
hydraulic device, the pressure sensor generating a signal in
response to a detected drop of pressure of the fluid below a
minimum pressure; and a signaling device responsive to the signal
generated by said the pressure sensor and generating a signal
perceivable by an operator when the pressure is below the minimum
pressure.
5. The apparatus according to claim 4, wherein the pressure sensor
comprises: a device that continuously closes an electrical circuit
when the monitored pressure is less than the minimum pressure.
6. The apparatus according to claim 1, wherein the supply of
hydraulic fluid is a hydraulic circuit normally supplying
pressurized hydraulic fluid to the hydraulic device in response to
a boom telescoping command.
7. The apparatus according to claim 1, wherein the supply of
hydraulic fluid is an auxiliary hydraulic circuit separate from the
circuit normally supplying pressurized hydraulic fluid to the
hydraulic device.
8. The apparatus according to claim 1, further comprising: a
one-way valve connected to an output port of the apparatus
preventing fluid from flowing from the hydraulic device controlling
extension of the telescoping boom back to the apparatus.
9. The apparatus according to claim 1, further comprising: a relief
valve controlling pressure in the fluid provided from the apparatus
to the hydraulic device controlling extension of the telescopic
boom.
10. A method of compensating for fluid contraction in a hydraulic
powered telescoping boom, the method comprising: monitoring the
elevation angle of the telescoping boom, and supplying fluid to a
hydraulic device controlling extension of the telescoping boom when
the elevation angle exceeds a predetermined threshold angle.
11. The method according to claim 10, comprising supplying fluid to
a hydraulic device controlling extension of the telescoping boom
when the elevation angle of the boom is at least thirty-five
degrees elevation above horizontal.
12. The method according to claim 10, further comprising:
generating a signal when the elevation angle of the boom exceeds
the threshold angle; and actuating a control in response to the
signal to supply hydraulic fluid to the hydraulic device.
13. The method according to claim 12, further comprising: opening a
fluid connection to permit flow of fluid into the hydraulic device;
and controlling pressure of fluid supplied to the hydraulic
device.
14. The method according to claim 12, further comprising:
monitoring the pressure of the fluid supplied to the hydraulic
device; generating a pressure signal when pressure in the fluid is
below a minimum pressure; and generating a notification perceivable
by an operator in response to the pressure signal.
15. The method according to claim 10, further comprising supplying
fluid to a hydraulic device controlling extension of the
telescoping boom in a flow direction when the elevation angle
exceeds a predetermined threshold angle, and preventing the fluid
from flowing in reverse of the flow direction.
16. A compensating device for compensating for fluid contraction in
a hydraulic powered telescoping boom of a crane, the crane
including an extensible boom and a hydraulic device for extending
the boom, the compensating device including: a monitor determining
the elevation angle of the telescoping boom; a supply of
pressurized hydraulic fluid including a reservoir of hydraulic
fluid; an inlet connectable to the supply of pressurized hydraulic
fluid; a fluid control controlling flow of fluid through the inlet
and responsive to the monitor determining the elevation angle of
the telescoping boom; an outlet connectable to the hydraulic device
and supplying pressurized hydraulic fluid received via the inlet
and fluid control to the hydraulic device; and a second connection
connectable to the reservoir of hydraulic fluid and establishing a
return flow path permitting a portion of the fluid provided to the
hydraulic device to return to the reservoir.
17. The compensating device according to claim 16, wherein the
fluid control comprises a valve responsive to the monitor and
controlling flow of fluid from the inlet to the hydraulic device of
the crane, and the fluid control enables fluid flow to the
hydraulic device when the elevation angle exceeds a predetermined
threshold angle.
18. The compensating device according to claim 16, further
comprising: a pressure sensor monitoring pressure of the hydraulic
fluid between the inlet and the hydraulic device and generating a
pressure signal when the pressure is below a minimum pressure; and
a warning device generating a signal perceivable by an operator
responsive to the signal generated by the pressure sensor.
19. The compensating device according to claim 16, further
comprising: a one way check valve positioned between the inlet and
the hydraulic device for preventing flow of fluid from the
hydraulic device back to the inlet.
20. The compensating device according to claim 16, further
comprising: a valve operatively connected to the second connection
to selectively permit flow of pressurized hydraulic fluid to the
second connection and to the reservoir.
21. The compensating device according to claim 20, wherein the
valve is a pressure relief valve for limiting the pressure of the
pressurized hydraulic fluid provided to the hydraulic device.
Description
[0001] This application claims priority to Provisional Application
61/202,030 filed on Jan. 21, 2009, the entirety of which is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] Load lifting devices such as cranes, and especially mobile
cranes, often use telescoping booms to achieve the necessary lift
height. A telescoping boom is made up of multiple sections which
telescope with respect to one another to change the overall length
of the boom. The telescoping boom of a portable crane is often
extended by one or more hydraulic devices, typically cylinders,
acting on the sections of the boom. Fluid is supplied to, or
removed from, a hydraulic cylinder to cause a piston to move within
the hydraulic cylinder. Movement of the piston enables the boom of
the load lifting device to extend or contract.
[0003] A natural phenomenon is known to occur in telescoping booms,
caused by thermal expansion and the subsequent contraction of fluid
in the hydraulic cylinder supporting the boom. This natural
phenomenon may be observed when a load lifting device is operated
for extended periods of time causing the fluid in the hydraulic
cylinder to heat up and subsequently cool down. Hydraulic fluid
expands when it is heated and contracts when it is cooled. A load
lifting device may be left idle for a period of time during which
the fluid cools down. During such time the elevation angle of the
boom above horizontal may be relatively low. In this instance, when
the fluid cools it contracts but the boom may sometimes not retract
because of frictional forces acting between individual boom
sections. This effect varies depending on the particular boom
configuration, the level of friction between individual sections of
the boom, lubrication of the boom sections, and other possible
environmental factors. Thus, the telescoping boom could remain
extended even though the boom sections are not fully supported by
fluid in hydraulic cylinders.
[0004] In the described situation the relative positions of the
boom sections might be supported by friction between individual
sections of the boom. If the lifting machine operator elevates the
boom from the low elevation angle position the boom will remain at
the same boom length for a certain range of elevation angles.
However, if the operator continues to elevate the boom, the boom
will eventually reach an elevation angle where the weight of the
boom sections or a combination of the weight of the sections and
any other load overcomes the friction between boom sections. At
this point, the boom may retract until the column of fluid in the
cylinders again fully supports the boom sections. As can be
appreciated, this uncommanded boom retraction is undesirable. The
present invention provides a system and a method for avoiding this
undesirable situation.
SUMMARY OF THE INVENTION
[0005] The apparatus and method of the invention compensates for
fluid cooling and contraction, as described, while avoiding the
potential for operator errors. This invention avoids uncommanded
boom retraction without requiring manual operator intervention or a
high pressure source of hydraulic fluid. The invention additionally
comprises a device that can be advantageously easy to retrofit into
existing crane or it may be incorporated in a crane at the time of
original manufacture.
[0006] The invention requires only a relatively low-pressure source
of hydraulic fluid which is often part of an existing lifting
machine The hydraulic source for the invention can also be provided
as an add-on or auxiliary to the existing hydraulic system of a
crane. Furthermore, the apparatus and method of the invention
avoids the need for re-synchronizing the boom sections of a crane
because the invention replenishes fluid in hydraulic cylinders
without changing the boom extension. The boom sections are properly
synchronized when the boom is originally extended and the boom
extension length does not change significantly when the fluid in
the hydraulic cylinders is replenished according to the present
invention.
[0007] An apparatus for compensating for fluid contraction in a
hydraulic powered telescoping boom according to the invention may
include a monitor determining the elevation angle of the
telescoping boom, a supply of hydraulic fluid, and a fluid control
responsive to the monitor for providing hydraulic fluid from the
supply to a hydraulic cylinder or equivalent device controlling
extension of the telescoping boom when the boom elevation angle
exceeds a predetermined threshold angle. A threshold angle of
thirty-five degrees above horizontal may be a typical setting in
accordance with the invention as this is representative of an angle
below which frictional forces may be significant in retaining the
relative positions of booms sections in many cranes while, above
that angle the frictional forces may no longer retain the boom
sections against their own weight and/or other imposed loads.
[0008] The apparatus may also include a control valve configured to
supply hydraulic fluid to the hydraulic cylinder in response to a
signal generated by the monitor when the elevation angle of the
boom exceeds the threshold angle.
[0009] The apparatus may further include a pressure sensor
monitoring pressure of the fluid provided to the hydraulic cylinder
and generating a signal in response to a detected drop of pressure
below a minimum pressure. Further, a device generating a signal
perceivable by an operator responsive to the signal generated by
said pressure sensor may also be included. In a preferred
embodiment it may be desirable to use a pressure sensor which
continuously closes an electrical circuit unless the monitored
pressure exceeds the desired minimum.
[0010] The invention calls for a supply of hydraulic fluid
providing fluid to the apparatus at an appropriate pressure at
least high enough to support the boom. In typical applications,
this pressure may be about 200 PSI. This supply may also be the
hydraulic circuit which powers the telescoping extension cylinders
as part of normal boom extension, or it may be a different or
auxiliary hydraulic supply. In one example, the supply of hydraulic
fluid may be a hydraulic circuit providing hydraulic fluid to a
wind speed indicator.
[0011] The apparatus may also include a pressure reducing relieving
valve controlling pressure of fluid supplied by the invention. This
may be accomplished by releasing a portion of the hydraulic fluid
back to a hydraulic fluid reservoir.
[0012] The apparatus may further include a one-way valve fluidly
connected to an output port of the apparatus. This prevents
back-flow of fluid and, thus, isolates normal operation of the
telescoping boom, such as extension and retraction, from the
compensation function of the invention.
[0013] According to the invention, a method of compensating for
fluid contraction in a hydraulic powered telescoping boom may
include monitoring the elevation angle of the telescoping boom and
supplying fluid to a hydraulic cylinder controlling extension of
the telescoping boom when the elevation angle exceeds a
predetermined threshold angle. The threshold angle may be set at
thirty-five degrees above horizontal or at other angles suitable to
individual cranes.
[0014] The method may further include generating a signal when the
elevation angle of the boom exceeds the threshold angle and
energizing a control valve in response to the signal to supply
hydraulic fluid to the hydraulic cylinder. In an embodiment the
method could additionally include opening a fluid connection
controlled by the control valve into the hydraulic cylinder.
Pressure of fluid supplied to the hydraulic cylinder may be
controlled by releasing fluid through a relief valve.
[0015] The method could also include monitoring for any drop of
pressure of the hydraulic fluid being supplied to the hydraulic
cylinder, and generating a signal in response to the detected drop
of pressure. A notification perceivable by an operator can be
generated in response to the low pressure signal. In an
advantageous embodiment the signal can be continuously generated
unless the pressure of the hydraulic fluid being supplied to the
hydraulic cylinder exceeds the desired minimum. A one-way valve may
be provided to prevent a reverse of flow of fluid in the device and
method of the invention.
[0016] An advantage of a device in accordance with the invention is
that it is easily retrofit in a lifting device with a hydraulic
powered telescoping boom. The inventive device may include a
pressure source such as a pump, or it may utilize components
already in place on a crane.
[0017] The foregoing is a summary and thus contains, by necessity,
simplifications, generalization, and omissions of detail.
Consequently, those skilled in the art will appreciate that the
summary is illustrative only and is not intended to be in any way
limiting. Other aspects, features, and advantages of the devices
and/or methods of the invention will become apparent in the
teachings set forth herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The foregoing and other features and advantages of the
present invention will become more fully apparent from the
following description and appended claims, taken in conjunction
with the accompanying drawings wherein:
[0019] FIG. 1 is a schematic example of a telescoping boom of a
lifting machine;
[0020] FIG. 2 is a schematic illustration of a compensating
apparatus according to an exemplary embodiment of the
invention;
[0021] FIG. 3 is a schematic example of a hydraulic cylinder;
[0022] FIG. 4 depicts an example of an implementation of the
compensating apparatus according to the invention;
[0023] FIG. 5 is a flow chart describing a process according to an
exemplary embodiment of the invention;
[0024] FIG. 6 is a flow chart describing an example of process
steps according to an aspect of the invention; and
[0025] FIG. 7 is a flow chart describing a process of detecting a
system failure according to an example of the invention.
DETAILED DESCRIPTION
[0026] FIG. 1 illustrates an example of a telescoping boom 110.
Boom sections 120 are configured in a telescoping configuration and
may be extended and retracted by one or more hydraulic cylinders,
only one hydraulic cylinder 130 being shown. The boom extension
controller 140 controls actuation of individual hydraulic cylinders
130 to achieve a desired boom extension length and appropriate
extension sequencing. Telescoping boom 110 is shown as elevated at
a certain elevation angle above horizontal. According to the
invention, compensating apparatus 100 compensates for hydraulic
fluid cooling which could cause uncommanded boom retraction.
[0027] FIG. 2 schematically illustrates an exemplary embodiment of
the compensating apparatus 100. Elevation angle monitor 200 detects
the elevation angle of the telescoping boom 110 above horizontal.
When the elevation angle exceeds a predetermined threshold, it
supplies a signal to a fluid control 220. Fluid control 220 may be
implemented as a normally-closed position two-way solenoid valve.
Thus, the valve, when closed, prevents any hydraulic fluid supplied
by supply 210 from reaching the rest of a hydraulic circuit that
extends and retracts the boom.
[0028] Once elevation monitor 200 supplies a signal to the fluid
control 220, the control opens a fluid connection from the supply
210. If 220 is a solenoid valve, this can be accomplished, for
example, by simply actuating the solenoid. As shown in FIG. 2, the
pressure of the fluid in the circuit may be regulated by pressure
reduction means 230. Pressure reduction means 230 may be a relief
valve configured to release fluid exceeding a predetermined
pressure threshold or any device providing the same function.
[0029] In an exemplary embodiment, the pressure relief valve may be
set for 200 PSI (pounds per square inch). Thus, hydraulic fluid
which is provided at a higher pressure than 200 PSI will be
released into reservoir 240. Reservoir 240 is an overflow reservoir
of hydraulic fluid, which can then be reused in the hydraulic
circuit as it is again pressurized and recycled throughout the
system. Thus, reservoir 240 can provide fluid back to supply
210.
[0030] The hydraulic fluid downstream of valve 230 is regulated to
a desired pressure, approximately 200 PSI in the example given. Of
course, it should be understood that 200 PSI is a value used in an
example embodiment implemented with a particular lifting machine
configuration and is not in any way limiting. For different lifting
machine configurations the appropriate pressure can be determined
experimentally or through modeling.
[0031] The exemplary embodiment uses 200 PSI as the replenishing
pressure to the cylinders. This value was arrived at by
experimentation to determine a value which would support the weight
of the boom in its extended configuration, but would not further
extend the cylinder or the boom without a specific boom extend
command. As can be appreciated, friction plays a great role in the
system. Thus, in the exemplary embodiment, 200 PSI is not
sufficient to overcome the friction between boom sections and,
thus, will not extend the boom. On the other hand, this pressure is
sufficient to support the boom in its existing configuration having
already been extended.
[0032] The supply 210 illustrated in FIG. 2 is a source of
pressurized hydraulic fluid. This may be obtained from a variety of
sources. Supply 210 may be a hydraulic line from a swing parking
brake release function on the swing, steering, and auxiliary
manifold of the crane. The supply may also be the source which is
used to power a wind speed indicator when the crane is equipped
with that option. However this does not limit the source to only
such options and it could be powered by many other sources of
high-pressure hydraulic fluid already present on the lifting
machine, or by a dedicated pump connected to a reservoir of
hydraulic fluid. It is advantageous to use a source of hydraulic
fluid which gets pressurized immediately when the lifting machine
is turned on. This type of fluid source will immediately provide
pressure without any operator input, thus avoiding the possibility
of operator error in forgetting to power on the compensation
apparatus.
[0033] The supply 210 may provide fluid at a pressure from another
hydraulic source that is higher than needed for the compensation
system, i.e., at 250 PSI, as soon as the engine of the lifting
machine is started. Thus, fluid control 220 will receive a constant
source of high-pressure hydraulic fluid immediately when the engine
is started. Indeed, this is advantageous as the system is
automatically powered on immediately when the engine is started,
which is always done as the first thing when operating the lifting
machine.
[0034] Elevation angle monitor 200 monitors the elevation angle of
the telescoping boom above the horizontal. The elevation angle
monitor 200 may be implemented as an analog sensor, a digital
sensor, or an output of the lifting machine control computer. The
particular implementation is not limiting. The elevation angle
monitor 200 continuously detects the boom elevation angle and
commands the fluid control 220 to provide fluid to the rest of the
circuit when a predetermined elevation angle threshold is exceeded.
Thus, at elevation angles which are lower than the threshold angle,
the fluid control 220 remains closed and no fluid is supplied to
the rest of the circuit. However, once the threshold angle is
exceeded, fluid control 220 opens and provides fluid to the rest of
the circuit, thus supplying recharging fluid through a check valve
260 to a hydraulic cylinder powering the telescoping boom. If there
are multiple hydraulic cylinders powering the boom, a corresponding
multiple of valves 260 may be provided, one for each cylinder.
[0035] It is important that elevation monitor 200 not command
opening of valve 220 too early because it has been shown that even
a very small amount of pressure (less than 15 PSI) is enough to
extend a telescoping boom at a very low elevation angle. Therefore,
the elevation monitor 200 should not permit flow through the rest
of the compensation system until a predetermined elevation angle is
reached. In a particular crane apparatus it has been determined
that, at elevation angle of 35.degree., supplying a compensating
flow of fluid at 200 PSI supports the boom in its already extended
configuration but does not further extend the telescoping boom. The
specific angle appropriate for achieving this balance in any
particular crane will depend on the mass of the crane boom
sections, the friction acting between adjacent telescopic boom
sections, the pressure of fluid available to the compensation
system and the desired operating pressure, and other factors
affecting the individual model crane. The threshold angle to be
detected by monitor 200 will have to be determined empirically for
each model crane and set to actuate the compensation system of the
invention at an angle of elevation whereat the boom is supported
but does not expand undesirably.
[0036] Uncommanded boom retraction has been often observed at boom
elevation angles exceeding 60.degree. above horizontal. Thus, the
threshold angle at which the compensating apparatus starts
providing replenishing fluid must be lower than 60.degree. in
mostly any crane. To minimize the chance of boom retraction, the
threshold angle should be set at the lowest angle at which the
replenishing fluid (at available or set pressure) does not extend
the boom without a specific boom extend command from the crane
controls. Accordingly the threshold angle was set to 35.degree. in
a preferred embodiment.
[0037] The one-way valve 260 ensures that fluid supplied by the
recharge circuit only flows in one direction, from the
recharge/compensation circuit to the boom cylinder. The output port
270 then supplies fluid to the hydraulic cylinder 130. As shown in
FIG. 1, the compensating apparatus may share a fluid connection
with boom extension controller 140. Thus, the one-way valve 260
prevents back flow of hydraulic fluid through the recharge circuit
when the boom extension controller 140 extends the boom and, thus,
isolates the normal boom control function from the operation of the
invention. Further, as shown in FIG. 2, the recharge circuit may
include multiple one-way valves and multiple output ports, as
appropriate for the relevant lifting machine.
[0038] As noted above, output port 270 is fluidly connected to a
hydraulic cylinder 130 and the connection may be shared with the
boom extension controller 140. Alternatively, port 270 may be
connected to the cylinder via a dedicated port on the piston-side
of the hydraulic cylinder 130.
[0039] The recharge circuit illustrated in FIG. 2 may also include
a pressure sensor switch 250. Pressure sensor switch 250 may be
implemented as a normally-closed pressure switch which opens an
electrical connection when it detects a pressure above a certain
threshold. Thus, pressure sensor switch 250 remains closed (keeping
an electrical connection closed) unless it detects a pressure above
a threshold. The electrical output of pressure sensor switch 250
may be connected to a signaling device which outputs a perceivable
signal, such as a sound or optical signal perceivable by an
operator. Thus, the operator of the lifting machine is notified by
the perceivable signal that the pressure detected by pressure
sensor switch 250 is below the threshold pressure. It is
advantageous to use a normally closed pressure switch because it is
very robust against failure of the pressure monitoring system. In
other words, the pressure monitoring system indicates a failure to
the operator unless it detects pressure above the threshold. Thus,
if the pressure sensor switch 250 fails (such that it no longer can
properly detect pressure), it will still indicate a failure to the
operator.
[0040] FIG. 3 illustrates an example of a hydraulic cylinder 130
controlling extension of a telescoping boom. Piston-side 310
receives hydraulic fluid through a port to control extension and
contraction of hydraulic cylinder. Rod-side 320 may also receive
hydraulic fluid to control contraction of the hydraulic cylinder.
Although only two ports are illustrated in FIG. 3, it is understood
that additional ports may be present in the hydraulic cylinder.
Fluid for compensating for thermal contraction would normally be
input to the piston side 310 to maintain the extended state of the
boom, as discussed above.
[0041] FIG. 4 illustrates one example of an implementation of the
compensating apparatus of the invention housed in a compact
aluminum manifold. As shown in FIG. 4, the manifold housing 400 may
be a simple box-shape and includes a number of openings. Fluid
control 220 is connected to one of these openings. Pressure
reduction means 230 (implemented as a pressure reducing valve) is
connected to another one of the openings and includes a port
fluidly connectable to reservoir 240. Further, pressure sensor
switch 250 is connected to another one of the openings and is
configured to sense pressure inside the manifold 400. One or more
output ports 270 are provided through additional openings in the
manifold 400. Manifold 400 also includes supply input 410 which is
fluidly connected with supply 210. Further, the manifold also
includes supply return 420 which outputs fluid provided through
supply input 410. Thus, the manifold 400 can be advantageously
connected in-line with an existing hydraulic fluid line with
minimal impact on the existing hydraulic fluid line. Furthermore,
manifold 400 may also include one or more diagnostic ports 430
which enable monitoring of pressure and/or temperature inside the
manifold 400.
[0042] As can be understood from FIGS. 2 and 4, the compensating
apparatus may be implemented as a device or kit that may be
retrofit to an existing lifting machine. Further, the example
embodiment illustrated in FIG. 4 is advantageously robust, compact,
and efficient to manufacture. Of course, the compensating apparatus
is not limited in any way to the implementation shown in FIG. 4,
but may be adapted to the particular application at hand, to the
relevant lifting machine being retrofitted, or to conveniences in
manufacturing and/or installation.
[0043] FIG. 5 schematically illustrates steps of a process for
compensating for fluid contraction in a hydraulic powered
telescoping boom. In step S 500, the elevation angle of the boom is
detected. In step S 510, the elevation angle is compared to a
predetermined threshold. In an example implementation the threshold
angle was 35.degree. above horizontal. If the elevation angle does
not exceed the predetermined threshold angle, the process returns
to detecting the boom elevation angle. Thus, the elevation angle is
continuously monitored. When the elevation angle exceeds the
threshold, fluid is supplied to hydraulic cylinders in step S 520.
After fluid is supplied to hydraulic cylinders, the elevation angle
of the boom is again detected, and continuously monitored. Thus, if
the elevation angle of the boom decreases to below the threshold,
the supplying of fluid to the cylinders is halted.
[0044] FIG. 6 illustrates further details of step S 520. In step S
600 a control signal is passed to fluid controller 220, and, in an
exemplary embodiment, a control valve is energized. Fluid
controller 220 opens a fluid connection from supply 210 to the rest
of the compensating apparatus in step S 610. Further, in step S 620
the pressure is controlled (and may be reduced by a pressure
reduction means such as a pressure reducing relieving valve 230) to
a predetermined pressure level. In an exemplary embodiment the
pressure level may be set at 200 PSI, thus limiting the pressure
that is output from the compensating apparatus in step S 630 to 200
PSI. Further, in step S 630 the outputting of fluid may be
controlled such that the fluid is output in a single flow direction
and a reverse of flow direction is prevented (for example by using
a one-way valve such as 260).
[0045] Further, FIG. 7 illustrates a process of monitoring pressure
in a compensating apparatus. In step S 700, the drop in fluid
pressure is detected. In response to the detected drop in fluid
pressure, a signal is generated in step S 710. Further, in step S
720 a perceivable notification is output. In some implementations
it may be advantageous to continuously generate a notification
signal in step S 710 unless and until the detected pressure rises
above a predetermined threshold. This could be achieved, for
example, by using a normally-closed switch which opens when
pressure rises above the threshold.
[0046] The foregoing detailed description has set forth various
embodiments of the devices and/or processes via the use of block
diagrams, flowcharts, and/or examples. Insofar as such block
diagrams, flowcharts, and/or examples contain one or more functions
and/or operations, it will be understood by those within the art
that each function and/or operation within such block diagrams,
flowcharts, or examples can be implemented, individually and/or
collectively, by a wide range of particular implementations. Thus,
the example implementations are not limiting but rather illustrate
a contemplated approach to solve a problem identified by the
inventors.
[0047] Those skilled in the art will recognize that it is common
within the art to describe devices and/or processes in the fashion
set forth herein, and thereafter use engineering practices to
integrate such described devices and/or processes into a larger
system or systems. That is, at least a portion of the devices
and/or processes described herein can be integrated into a
mechanical system via a reasonable amount of experimentation.
[0048] With respect to the use of substantially any plural and/or
singular terms herein, those having skill in the art can translate
from the plural to the singular and/or from the singular to the
plural as is appropriate to the context and/or application. The
various singular/plural permutations may be expressly set forth
herein for sake of clarity.
[0049] While various aspects and embodiments have been disclosed
herein, other aspects and embodiments will be apparent to those
skilled in the art. The various aspects and embodiments disclosed
herein are for purposes of illustration and are not intended to be
limiting, with the true scope and spirit being indicated by the
following claims.
* * * * *