U.S. patent application number 13/689733 was filed with the patent office on 2013-08-15 for auxiliary flow valve system and method for managing load flow requirements for auxiliary functions on a tractor hydraulic system.
This patent application is currently assigned to VANGUARD EQUIPMENT, INC.. The applicant listed for this patent is VANGUARD EQUIPMENT, INC.. Invention is credited to David V. Hart.
Application Number | 20130205762 13/689733 |
Document ID | / |
Family ID | 48536072 |
Filed Date | 2013-08-15 |
United States Patent
Application |
20130205762 |
Kind Code |
A1 |
Hart; David V. |
August 15, 2013 |
AUXILIARY FLOW VALVE SYSTEM AND METHOD FOR MANAGING LOAD FLOW
REQUIREMENTS FOR AUXILIARY FUNCTIONS ON A TRACTOR HYDRAULIC
SYSTEM
Abstract
A system and method for managing hydraulic fluid load flow
requirements for a tractor having a single pump hydraulic system.
The system and method controls an implement hydraulic system and an
auxiliary implement hydraulic system using a single hydraulic pump.
The auxiliary flow valve system and method of the present
disclosure gives precedence to the auxiliary functions so as to
maintain full function of the auxiliary device. It also may supply
a reduced flow, less than the maximum available from the system
hydraulic pump to the auxiliary device. The remaining flow is
available to the implement hydraulic system, with full flow being
available to the implement when no auxiliary function is used. It
also provides the ability to use a closed center valve in a load
sensing system by bleeding flow pressure from the auxiliary
hydraulic system.
Inventors: |
Hart; David V.; (Vancouver,
CA) |
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Applicant: |
Name |
City |
State |
Country |
Type |
VANGUARD EQUIPMENT, INC.; |
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US |
|
|
Assignee: |
VANGUARD EQUIPMENT, INC.
Tulsa
OK
|
Family ID: |
48536072 |
Appl. No.: |
13/689733 |
Filed: |
November 29, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61564690 |
Nov 29, 2011 |
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Current U.S.
Class: |
60/327 |
Current CPC
Class: |
F15B 2211/4053 20130101;
F15B 11/162 20130101; F04B 49/00 20130101; F15B 13/022 20130101;
F15B 2211/781 20130101 |
Class at
Publication: |
60/327 |
International
Class: |
F04B 49/00 20060101
F04B049/00 |
Claims
1. A process for managing fluid flow requirements for a tractor
auxiliary hydraulic system and an implement hydraulic system
connected in parallel to a single pump hydraulic system,
comprising: obtaining an implement (pipelayer) fluid pressure
requirement from the implement (pipelayer) hydraulic system;
obtaining an auxiliary implement fluid pressure requirement;
determining a greatest system pressure requirement; transmitting
the greatest system pressure requirement to the single pump
hydraulic system; obtaining fluid flow from the single pump
hydraulic system to maintain the greatest system pressure
requirement; and maintaining fluid flow to satisfy the auxiliary
implement fluid pressure requirement independent of the implement
(pipelayer) system fluid pressure requirement.
2. The process of claim 1 further restricting the auxiliary fluid
flow to the auxiliary hydraulic system to a predetermined
valve.
3. The process of claim 2 wherein the single pump hydraulic system
includes a maximum pump capacity and wherein said predetermined
valve is less than said maximum pump capacity.
4. The process of claim 3 wherein the maximum pump capacity minus
the predetermined valve of the restricted fluid flow to the
auxiliary hydraulic system is greater than or equal to the fluid
pressure requirement of the implement hydraulic system.
5. The process of claim 1 wherein fluid flow is provided to the
implement hydraulic system necessary to satisfy the implement
hydraulic system fluid pressure requirement.
6. The process of claim 5 wherein when the auxiliary hydraulic
system is not in use the greatest system pressure requirement will
be equal to the implement fluid pressure requirement.
7. The process of claim 1 wherein fluid flow is bled from the
auxiliary hydraulic system.
8. The process of claim 2 wherein fluid flow is bled from the
auxiliary hydraulic system.
9. The process of claim 8 wherein the fluid flow bled from the
auxiliary hydraulic system is less than said predetermined
valve.
11. A process for managing fluid flow requirements for an auxiliary
implement hydraulic system and an implement hydraulic system
connected in parallel to a single pump hydraulic system,
comprising: obtaining an implement fluid pressure requirement from
the implement hydraulic system; obtaining an auxiliary implement
fluid pressure requirement from the auxiliary implement hydraulic
system; determining a greatest system pressure requirement;
transmitting said greatest system pressure requirement to the
single hydraulic pump; obtaining fluid flow from said single
hydraulic pump to maintain said greatest system pressure
requirement; maintaining an essential operation fluid flow to
satisfy said essential operation fluid pressure requirement
independent of said implement fluid pressure requirement; and
restricting the auxiliary fluid flow to the auxiliary hydraulic
system to a predetermined valve.
11. The process of claim 10 wherein the single pump hydraulic
system includes a maximum pump capacity and wherein said
predetermined valve is less than said maximum pump capacity.
12. The process of claim 11 wherein the maximum pump capacity minus
the predetermined valve of the restricted fluid flow to the
auxiliary hydraulic system is greater than or equal to the fluid
pressure requirement of the implement hydraulic system.
13. The process of claim 10 wherein fluid flow is provided to the
implement hydraulic system necessary to satisfy the implement
hydraulic system fluid pressure requirement.
14. The process of claim 10 wherein fluid flow is bled from the
auxiliary hydraulic system.
15. The process of claim 14 wherein the fluid flow bled from the
auxiliary hydraulic system is less than said predetermined valve.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims the priority of U.S. Provisional
Patent Application No. 61/564,690 filed Nov. 29, 2011, herein
incorporated by reference in its entirety for all purposes.
FIELD OF THE INVENTION
[0002] The present invention relates to land vehicle hydraulic
systems generally and more specifically to pipelayer hydraulic
assemblies mounted to track-type tractors.
BACKGROUND OF THE INVENTION
[0003] Hydraulic track-type pipelayers consist of a track-type
crawler tractor with a pipelayer draw works structure mounted to
it, along with the associated hydraulic hook and boom winches, the
winch hydraulic-controls, and all the necessary rigging (per ISO
8813=mechanism to position the boom and hook). The track-type
crawler tractor provides the power to drive the hydraulic winches,
and any other hydraulic system fitted or used to control the
crawler tractor.
[0004] The pipelayer (implement) hydraulic system can be driven
either directly with a dedicated implement pump supplying only the
pipelayer system, or connected in parallel with the tractor
hydraulic implement system. The tractor implement system is also
arranged in parallel. A parallel system means that when hydraulic
functions are actuated simultaneously, hydraulic fluid flow is
divided to each function. It is known however, that there will be a
greater flow to the path with the least resistance. Due to this
fact, when the pipelayer implement is connected to the tractor
implement system in parallel, either the tractor implement system
or the pipelayer system could be impaired when used simultaneously.
This is because the fluid directed to the path of least resistance
could leave the other system with insufficient hydraulic pressure
to adequately operate that system. This is typically not an issue
with the pipelayer system, since all other existing
implements--bulldozer cylinders, rippers, tow winches, etc.--are
typically either removed or disconnected, or are not used during
critical pipelaying operations. The same is not true, however, for
essential hydraulic operations such as the tractor steering system
and certain other auxiliary hydraulic systems.
[0005] Crawler tractors have two methods for steering control:
mechanical steering clutches, or hydraulic differential steering.
Mechanical steering clutches are completely separate from the
hydraulic implement system, and are unaffected by it. Hydraulic
differential steering systems use a hydraulic steering motor to
facilitate a change of direction. The hydraulic steering motor can
be powered either by its own dedicated pump, separate from the
implement system (a two-pump system), or by the tractor implement
pump (a single-pump system).
[0006] In a single pump system, the steering function could be
severely compromised unless it is given precedence over the other
tractor implement functions. With a pipelayer connected directly to
a single-pump system which also services the steering function, the
steering of the tractor could be drastically impaired if a load
placed by the pipelayer implement consumes hydraulic flow, leaving
insufficient flow for the steering function. For example, if the
tractor was making a turn while quickly raising an empty hook, the
hook winch would have a very low pressure requirement (least
resistance) while having a high flow requirement. In this example,
the majority of hydraulic fluid would flow through the pipelayer's
hook circuit, leaving significantly less, and potentially
insufficient, flow for the steering function. This is an extremely
undesirable situation. For this type of reason, single pump
differential steering systems have not been successfully
implemented on tractors including implements such as pipelayers,
and therefore pipelayers have been primarily used on crawler
tractors with mechanical steering clutches. A need, therefore,
exists for a single pump differential steering system and method
for a tractor including hydraulic implement, such as a pipelayer
connected in parallel thereto, wherein the tractor steering system,
or any other essential hydraulic system, is not affected by the
hydraulic flow requirements of the implement (pipelayer).
[0007] Auxiliary implements may also be connected to the tractor
hydraulic system in addition to the implement hydraulic system.
Auxiliary implements may include a pipelayer counterweight used to
counter (or balance) the weight forces exerted on one side of the
tractor by the weight of the draw works structure (plus the weight
of the pipe or other apparatus which may be supported therefrom).
Traditionally, pipelayer tractor hydraulic systems have used a
small dedicated pump, most commonly of a fixed displacement type,
to supply the hydraulic flow requirements of the auxiliary
implement which is separate from the main draw works implement pump
(or pumps in dedicated pump, or two-pump draw works systems). A
need also exists for a load flow management system for a tractor
having a hydraulic implement and a hydraulic auxiliary implement in
a single pump hydraulic system so as to not affect the hydraulic
flow requirements of the auxiliary implement by the hydraulic flow
requirements of the implement.
SUMMARY OF THE INVENTION
[0008] The auxiliary flow valve system and method of the present
disclosure controls an implement hydraulic system such as a
pipelayer draw works structure with an auxiliary implement, such as
a counterweight, or multiple auxiliary implements using a single
hydraulic pump. The present auxiliary load flow valve system and
process gives precedence to the auxiliary system (counterweight)
which is in hydraulic fluid communication with an implement system
(pipelayer), by allowing the hydraulic power (pressure and flow) to
be controlled in the auxiliary hydraulic system independently of
the hydraulic pressure requirements of the implement hydraulic
system. As a result, full control of the auxiliary hydraulic
operation is maintained regardless of the implement system demands.
A secondary function and sub-process also allows either the
auxiliary system, or the implement system, to dictate the pump's
supply-pressure output. As used herein, the term auxiliary system
or auxiliary implement shall include any hydraulic system which
relates to an additional or support implement operation and
function, such as, but not limited to, a hydraulic flow tractor
counterweight. Also as used herein, the term implement system shall
mean any tractor primary implement operation and function such as,
but not limited to, a hydraulic pipelayer draw works.
[0009] In its general form, the present disclosure includes a
process for managing fluid flow for a tractor implement and an
auxiliary implement connected in parallel to a single hydraulic
pump. The process includes the steps of determining the implement
fluid pressure requirement; determining the auxiliary implement
fluid pressure requirement; and maintaining the auxiliary implement
fluid pressure requirement by providing fluid flow to the auxiliary
implement regardless of the implement fluid pressure
requirement.
[0010] The hydraulic auxiliary flow valve of the present disclosure
allows the use of a single pump to supply both the implement
(pipelayer draw works) and auxiliary implements (tractor
counterweight and other auxiliary implements). It can be used with
a variable displacement load sensing pump, or a fixed-displacement
pump.
[0011] The auxiliary flow valve system and method of the present
disclosure may utilize the same or similar main-logic element as
described in our U.S. Utility patent application Ser. No.
12/843,835, incorporated fully herein by reference. The auxiliary
flow valve of the present disclosure, in contrast, gives precedence
to the auxiliary functions and supplies a reduced flow, less than
the maximum available from the main draw works implement pump, to
them; the remaining flow being available to the draw works, with
full flow being available to the draw works when no auxiliary
function is used. The auxiliary load flow valve system and method
of the present disclosure also provides the ability to use a closed
center valve--typically used with pipelayer counterweight
controls--in a load sensing system. The load flow valve system
described in our U.S. application Ser. No. 12/843,835 gives
precedence to the tractor's essential operations, such as the
steering, and does not describe the ability to use a closed center
valve, however, this functionality could be added externally to the
circuit. Another main difference with the valve system of the
present disclosure is that the amount of flow going to the
auxiliary hydraulic system is limited since it will never require
full pump flow, but still give it priority since it is more crucial
to operate when demanded the previous load-flow valve of the
previous disclosure gave complete priority to the steering system,
right up to complete pump flow if required. The valve system of the
present disclosure, the implement system will always be able to
operate even when the auxiliary system is at full speed
operation.
[0012] One of the main benefits of the auxiliary flow valve system
and the method of the present disclosure is that it eliminates the
need for additional pump drives which are increasingly difficult to
accommodate in confined tractor engine compartments. In addition,
since it may be mounted remotely from the engine drive, it provides
more flexibility for installation in tight confines over
traditional dedicated auxiliary hydraulic pump systems.
[0013] In a preferred embodiment, the present disclosure includes a
process for managing hydraulic fluid flow requirements for an
implement hydraulic system and an auxiliary hydraulic system
connected to a single hydraulic pump. The process, generally,
includes the steps of: [0014] (1) obtaining an implement
(pipelayer) fluid pressure requirement from the implement
(pipelayer) hydraulic system; [0015] (2) obtaining an auxiliary
implement fluid pressure requirement; [0016] (3) determining a
greatest system pressure requirement; [0017] (4) transmitting the
greatest system pressure requirement to the single pump hydraulic
system; [0018] (5) obtaining fluid flow from the single pump
hydraulic system to maintain the greatest system pressure
requirement; and [0019] (6) maintaining fluid flow to satisfy the
auxiliary implement fluid pressure requirement independent of the
implement (pipelayer) system fluid pressure requirement.
[0020] Further aspects, features, and advantages of the present
invention will be apparent to those of ordinary skill in the art
upon examining the accompanying drawings and upon reading the
following detailed description of the preferred embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 depicts a schematic diagram of a single pump parallel
hydraulic system including the apparatus and process of the present
disclosure.
[0022] FIG. 2 is a schematic diagram depicting the flow paths and
electrical components of the manifold of the valve system of the
present disclosure.
[0023] FIG. 3 is a top view of the manifold of the valve system of
the present disclosure.
[0024] FIG. 4 is a front side view of the manifold of the valve
system of the present disclosure.
[0025] FIG. 5 is a side view of the back side of the manifold of
the valve system of the present disclosure.
[0026] FIG. 6 is a front end view of the manifold of the valve
system of the present disclosure.
[0027] FIG. 7 is a back end view of the manifold of the valve
system of the present disclosure.
[0028] FIG. 8 is a bottom view of the manifold of the valve system
of the present disclosure.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] The system of the present disclosure in a preferred
embodiment connects a pipelayer hydraulic system to a single-pump
crawler tractor's implement valve in parallel. It gives precedence
to the tractor's auxiliary hydraulic system by allowing the
hydraulic power (pressure and flow) to be controlled to the
hydraulic auxiliary system independently of the hydraulic pressure
requirements of the implement hydraulic system. In this way, full
control of the auxiliary device is maintained regardless of the
implement hydraulic system's demands. A secondary function also
allows either the auxiliary system or the implement system to
dictate the pump's supply-pressure output. Without the system of
the present disclosure installed, control of the auxiliary device
and the implement would be unreliable with a hydraulic pipelayer
system installed.
[0030] With reference to FIG. 1, a tractor hydraulic auxiliary
system connected to a pipelayer hydraulic system in parallel 10 is
disclosed. System 10 includes a tractor single-pump system 20, the
load flow hydraulic fluid flow manifold of the present disclosure
30, auxiliary hydraulic system 40, tractor implement hydraulic
system (such as a pipelayer) 50, and tractor hydraulic tank 60. In
system 10, of the present disclosure load-flow manifold 30 and
pipelayer system 50 are in a preferred embodiment connected to the
implement valve of a crawler tractor in parallel such that the
tractor single pump 20 is in fluid communication with load-flow
manifold 30, which is, in turn, in fluid communication with both
the auxiliary hydraulic system 40 and pipelayer hydraulic system
50. Single implement pump 20, auxiliary system implement 40, and
pipelayer system 50 are in fluid communication with tractor
hydraulic tank 60. The tractor auxiliary system may be any known
system such as a counterweight used in combination with a pipelayer
implement. Auxiliary counterweights of this kind may include a
hydraulic activation system, such as 40, in the present disclosure,
for manipulating the counterweight away from or toward the tractor
in order to counter the weight of the pipelayer system.
[0031] Hydraulic fluid is pumped by tractor single implement pump
20 from hydraulic tank 60, shown by flow diagram 22. Hydraulic
fluid is pumped by the tractor single pump 20 from hydraulic tank
20 into load flow manifold 30, as shown at 24. Load flow manifold
30 obtains the fluid flow pressure requirements of the tractor
auxiliary system and provides hydraulic fluid flow required to
auxiliary hydraulic system 40 necessary to actuate the auxiliary
implement such as a counterweight as described above, as shown at
26. Load flow manifold 30 also obtains the fluid flow pressure
requirements of implement (pipelayer) hydraulic system 50 and
provides fluid flow to pipelayer hydraulic system 50 at 28. Load
flow manifold 30 prioritizes the hydraulic fluid flow pressure
requirements of auxiliary implement hydraulic system 40 regardless
and independent of the fluid flow pressure demands of implement
(pipelayer) hydraulic system 50. Fluid is returned by tractor
auxiliary hydraulic system 40 to hydraulic tank 60, as shown at 32.
Fluid is returned by pipelayer hydraulic system 50 to hydraulic
tank 60, as shown at 34.
[0032] In a particular preferred embodiment, a crawler tractor with
a single implement pump having a maximum flow of 56 gpm may be
fitted with an implement system such as a hydraulic pipelayer draw
works and an auxiliary implement system such as a hydraulic
controlled counterweight. In such a system, the valve system 10 of
the present disclosure including an auxiliary load flow manifold 30
may be implemented. In this preferred embodiment the manifold 30
includes a closed center valve typically employed with pipelayer
counterweight controls in a load sensing system.
[0033] FIG. 2 is a flow and electrical schematic of the manifold 30
particularly suited in such an application. With reference to FIG.
2 taken in consideration with all the figures the operation of the
valve of the present disclosure shall next be described.
[0034] In operation, the tractor auxiliary hydraulic system 40
provides a signal 42 to load flow manifold 30 regarding the fluid
flow pressure required for proper auxiliary hydraulic system
function. Pipelayer system 50 provides a signal 44 to load flow
apparatus 30 regarding the fluid pressure requirement necessary for
operation of the pipelayer system. From auxiliary hydraulic system
pressure requirement signal 42 and pipelayer pressure requirement
signal 44, load flow manifold 30 determines the greatest system
pressure requirement 46 necessary for the proper function of
auxiliary hydraulic system 40 and/or pipelayer hydraulic system 50.
In a basic embodiment this is done by comparing the tractor
auxiliary hydraulic system pressure requirement contained in signal
42 with the pipelayer hydraulic pressure requirement (contained in
signal 44 to determine the larger-known as the greatest system
pressure requirement. In this way, either the auxiliary hydraulic
system or the implement hydraulic system may dictate the pump's
supply-pressure output.
[0035] Load flow manifold 30 provides a signal 46 to single
implement hydraulic pump 20 regarding this greatest system pressure
requirement. Load flow manifold 30 may include a microprocessor for
receiving signals 42 and 44 and for determining the greatest system
pressure requirement and generating greatest system pressure
requirement signal 46. This microprocessor may include as an output
for providing the greatest system pressure requirement signal 46 to
single pump system 20.
[0036] In a preferred embodiment the hydraulic fluid flow to the
auxiliary hydraulic system 40 may be restricted in a predetermined
manner such that it is less than the maximum hydraulic flow
available from the single implement pump 20 since many common
auxiliary hydraulic systems 40 do not require full pump flow. The
remaining hydraulic fluid flow is available to the implement
hydraulic system 50. Full hydraulic fluid flow is available to
implement hydraulic system 50 when the auxiliary hydraulic system
40 is not in use.
[0037] In addition the valve system of the present disclosure 10
provides the ability to use a closed center valve--typically used
with pipelayer counterweight controls--in a load sensing system. A
closed center valve is preferred in the present system because an
open center valve would always bleed off hydraulic flow to the
auxiliary hydraulic system which could affect the required
hydraulic flow to the implement hydraulic system and would
additionally generate undesired heat which may cause wear to the
components and other issues. In a closed center valve system as
used in the present preferred embodiment, in a load sensing
circuit, a bleed valve is inserted so as to slightly bleed the
auxiliary load sense circuit which would prevent false load sense
which otherwise may cause the system to malfunction. In a preferred
arrangement, the bleed system would be much smaller than the
restricted auxiliary flow system such that when the auxiliary
system is in operation, auxiliary flow would not be affected.
[0038] In response to the greatest system pressure requirement
contained in signal 46, the single implement hydraulic pump 20
provides the hydraulic fluid flow required to maintain the signaled
greatest system pressure at 52. Load flow manifold 30 receives the
hydraulic fluid flow required to maintain the greatest signaled
system pressure 52 from implement hydraulic pump 20. Load flow
manifold 30 prioritizes distribution of fluid flow to auxiliary
hydraulic system 40 at the required pressure 54. Load flow manifold
30 then provides hydraulic fluid flow to pipelayer hydraulic system
50. In this way, load flow manifold 30 maintains at all times the
required fluid flow to auxiliary hydraulic system 40 at the
required fluid pressure, regardless and independent of the
pipelayer hydraulic system 50. In the event that the pipelayer
system pressure requirement (per signal 44) of pipelayer hydraulic
system 50 is less than the auxiliary system requirement (per signal
42) of tractor steering system 40, load flow manifold 30 will
provide the necessary fluid flow to auxiliary hydraulic system 40
required to maintain the auxiliary hydraulic system pressure
requirement without a pressure drop due to fluid flow taking the
path of least resistance caused by the lower pressure request of
pipelayer hydraulic system 50. However, tractor auxiliary hydraulic
systems commonly do not require high flow and pressure to operate.
In this regard it may be disadvantageous to supply the maximum
pressure available to the auxiliary hydraulic system since it may
cause it to operate quicker than designed/desired/required and this
makes it more difficult to control.
[0039] When the hydraulic fluid flow enters the manifold 30 at 70,
a modulator valve 72 signals the flow and pressure required for the
respective systems. The modulator valve 72 further reduces the
greatest pressure from the implement pump 20 to the required
pressure of either the auxiliary hydraulic system 40 or the
pipelayer hydraulic system 50 (whichever is lower). The flow
pressure required by the pipelayer hydraulic system 50 is supplied
from manifold 30 through a pipelayer valve 74. The fluid pressure
required by the auxiliary hydraulic system 40 is supplied through
an auxiliary flow valve 76. However, since the auxiliary hydraulic
system 40 does not commonly require full pump flow resulting from
the priority afforded it, the hydraulic flow to the auxiliary
hydraulic system may be mechanically restricted at 78. For example,
in the preferred arrangement described herein, the flow to the
hydraulic system may be restricted to eight gallons per minute (8
gpm). Accordingly, a system including an implement pump 20 capable
of a maximum flow of 56 gpm giving priority to an auxiliary
hydraulic system of 8 gpm leaves 48 gpm available for the pipelayer
hydraulic system 50 through pipelayer valve 74. In this embodiment,
48 gpm will always be available to the pipelayer hydraulic system
which is capable of full operation at all times. It is understood,
however, that different embodiments could be constructed using
different maximum and restricted flow requirements such that the
flow to pipelayer hydraulic system 50 may be reduced to slow its
operation in certain embodiments.
[0040] In a closed center system employing a load sensing circuit
80, in fluid communication with modulator 72, includes a pump load
sense valve 82, a pipelayer load sense valve 84, an auxiliary load
sense valve 86 and a bleed load sense valve 88. The auxiliary
hydraulic system 40 in the preferred embodiment will include a
bleed valve 88 which includes a bleed restriction 90. Bleed
restriction 90 is a mechanical restriction of a desired structure.
In the preferred embodiment described herein, the bleed restriction
would allow 0.1 gpm to bleed from the auxiliary flow system. In
that the bleed of 0.1 gpm is much less than the restricted flow of
the auxiliary hydraulic system 40 of 8 gpm, when the auxiliary
hydraulic system 40 is in operation, the bleed is small enough so
as not to affect the function of the auxiliary hydraulic system
40.
[0041] Load flow apparatus 30 may provide the necessary fluid flow
to maintain the required system pressure in either auxiliary
hydraulic system 40 or pipelayer hydraulic system 50, depending on
which signals the greatest system pressure requirement, which then
becomes the greatest system pressure requirement contained in
signal 46. In this way, either the tractor steering system 40 or
the pipelayer system 50 may dictate the pump flow 52 required to
maintain the greatest system pressure (contained in signal 46).
Pump 20 is then actuated to provide the greatest system pressure 52
into load flow manifold as shown at 24. Load flow manifold 30 then
supplies the respective requisite flow and pressure to the
auxiliary hydraulic system and/or the implement (pipelayer) system.
When the auxiliary hydraulic system is not in use, full flow is
available to the implement hydraulic system.
[0042] Thus, the present invention is well adapted to carry out the
objects and attain the ends and advantages mentioned above as well
as those inherent therein. While presently preferred embodiments
have been described for purposes of this disclosure, numerous
changes and modifications will be apparent to those skilled in the
art. Such changes and modifications are encompassed within the
spirit of this invention as defined by the appended claims.
* * * * *