SYSTEME DE COMMANDE FLUIDIQUE

FLUID CONTROL SYSTEM

Abrégé anglais

Fluid Control System
Abstract of the Disclosure
A fluid control system has a first fluid pump
for supplying pressurized fluid in interrupted series
to first and second work elements. The first work
element in the series has priority which prevents
simultaneous full power operation of the first and
second work elements. A second fluid pump is capable
of supplying pressurized fluid to the second work
element only upon receiving a signal indicating that
pressurized fluid from the first pump is being directed
to the first work element. The subject fluid control
system is especially useful with a tree harvesting
machine where it is beneficial to propel the machine
and at the same time rotate the upper structure.

Revendications

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A fluid control system comprising:
first and second sources of pressurized fluid;
first, second, and third work elements;
first control means for selectively
controllably delivering pressurized fluid from said
first source to each of said first and second work
elements;
first signal means for transmitting a signal
only in response to pressurized fluid being delivered
to the first work element, said first signal means
including a pressure switch in fluid communication with
said first work element and actuated in response to
pressurized fluid being supplied to said first work
element, and a selector valve connected to said
pressure switch and activated by said signal; and
second control means for selectively
controllably delivering pressurized fluid from said
second source to the third work element and to the
second work element only in response to receiving said
signal.
2. The fluid control system, as set forth in
claim 1, including a pilot actuating system having a
third source of fluid pressure and a plurality of
actuating valves, said third source of fluid pressure
being controllably selectively deliverable to said
first and second control means by said actuating valves.
3. The fluid control system, as set forth in
claim 1, wherein said second control means includes a
flow control valve and limits the maximum amount of
pressurized fluid delivered from said second source to
said third work element.

4. The fluid control system, as set forth in
claim 1, wherein a controlled portion of the total
amount of said pressurized fluid from said second
source is simultaneously deliverable to said second and
third work elements.
5. A fluid control system comprising:
first, second, and third sources of
pressurized fluid;
first, second, and third work elements;
first and second control valves for
selectively controllably delivering pressurized fluid
from said first source to one of said first and second
work elements;
first signal means having a pressure actuated
switch in fluid communication with said first work
element and actuated in response to pressurized fluid
being supplied to said first work element for
transmitting a signal only in response to pressurized
fluid being delivered to the first work element, and a
selector valve connected to said pressure switch and
activated by said signal;
third and fourth control valves for
selectively controllably delivering pressurized fluid
from said second source to the third work element and
to the second work element only in response to
receiving said signal; and
pilot actuating means having a plurality of
actuating valves, said third source of pressurized
fluid being controllably selectively deliverable to
said first, second, third, and fourth control valves by
said actuating valves.

Description

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Description
Fluid Control System
Technical Field
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This invention relates generally to fluid
control systems and more particularly to a system which
selectively, controllably supplies pressurized fluid to
several work elements. Two separate fluid sources
within the fluid control system each controllably,
selectively supply pressurized fluid to a preselected
single work element under preselected conditions of
operation.
Background Art
In fluid control systems having a plurality of
work elements, it is common practice to provicJe the
work elements with pressurized fluld from a single
fluid source by interconnecting the control valves of
the work elements in an interrupted series circuit.
Certain ones of the work elements therefore have
priority over the other work elements. In such a
system, the work elements having less priority are
generally not operational when the work elements having
the greater priority are functionally operational. In
certain fluid control systems using interrupted series
circuits, the work elements having less priority may be
partially operational by modulation of the control
valves which control the higher priority work
elements. However, such systems are generally
inefficient and require difficult manipulation of the
fluid controls by the operator.
It is often desirable to operate several work
elements of a work vehicle simultaneously in order to
save time and energy and make a work operation more
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efflcient. To -this end, the several work elements can be pro-
vlded with separate fluid circuits having individual pumps and
controls. However, this increases the costs of the fluid control
system, adds weight and bulk to the overall machine, and repre-
sents waste.
The present invention is directed to overcoming one or
more of the problems as set forth above.
Summary of the Invention
In one aspect of the present invention there is provided
a fluid control system comprising: first and second sources of
pressurized fluid; first, second, and third work elements; first
control means for selectively controllably delivering pressurized
fluid from said first source to each of said first and second work
elements; first signal means Eor transmitting a signal only in
response to pressurized fluid being deLivered to the first work
element, said first signal means including a pressure switch in
fluid communication with said first work element and actuated in
response to pressurized Eluid heing supplied to said first work
element, and a selector valve connecte~ to s~id pressure switch
and activated by said signal; and second control means for
selectively controllably delivering pressurized fluid from said
second source to the third work element and to the second work
element only in response to receiving said signal.
According to another aspect of the invention there is
provided a fluid control system comprising: first, second, and
third sources of pressurized fluid; first, second, and third work
elements; first and second control valves for selectively con-
trollably delivering pressurized fluid from said first source to
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one of said first and second work elements; first signal means
having a pressure actuated switch in fluid communication with
said first work element and actuated in response to pressurized
fluid being supplied to said first work element for transmitting
a signal only in response to pressurized fluid being delivered to
the first work element, and a selector valve connected to said
pressure switch and activated by said signal; third and fourth
control valves for selectively controllably delivering pressurized
fluid from said second source to the third work element and to the
second work element only in response to receiving said signal; and
pilot actuating means having a plurality of actuating valves, said
third source of pressurized fluid being controllably selectively
deliverable to said firs-t, second, third, and fourth control
valves by said actuating valves.
Prior fluid control systems utilized an interrupted
series circuit to supply pressurized fluid from a single pump on
a priority basis to several work elements. However, a lesser
priority work element could not be operated, or could be operated
at less than full power, when a higher priority work element was
being used. In many instances, it would be advantageous to
operate at least two work implements of the priority system
simultaneously and at full power. The sub~ect invention provides
a solution to these problems by making a second pump available to
a lesser prior work element only when fluid from a first pump is
being utilized to operate a higher priority work element.
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Brief Description of the Drawing
The drawing is a diagrammatic view of an
embodlment of the present invention.
Best Mode for Carrying Out the Invention
Referring to the drawing, a fluid control
system 10 has a first source of pressurized fluid 12,
first and second work elements 14,16, and a first
control means 18 for controllably delivering
pressurized fluid to one of the first and second work
elements 14,16. Work element 14 is preferably a fluid
motor, such as a track motor, for driving the tracks of
a track-type machine, such as a tree harvester (not
shown). Work element 16 is preferably a fluid motor
such as a swing motor for rotating the upper portion of
a tree harvester (not shown). The first control means
13 has first and second control valves 20 and 22 for
controllably delivering pressurized fluid from the pump
12 to the work elements 14 and 16. Valves 20 and 22
are arranged in interrupted series which provides that
work element 14 has priority over work element 16.
Therefore, work element 16 cannol: normally be operated
when work element 14 is functioning. However,
simultaneous reduced speed operation of work element 16
is possible if all of the pressurized fluid is not
being used by work element 14 and the control valve 20
can be modulated.
The fluid control system 10 includes a first
means 23 for transmitting a signal 25 only in response
to pressurized fluid being delivered to the first work
element 14. The con-trol system 10 has a third work
element 2~, a second source of pressurized fluid,
including a pump 24, and a second means 27 for
delivering pressurized fluid from the second fluid
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source 24 to the second work element 16 only in
response to receiving the signal 25. The second means
27 includes a second control means 26.
The second control means 26 has third and
fourth control valves 30 and 32 which controllably
deliver pressurized fluid from the second source 24 to
the work element 28 and the work element 16, as will be
hereinafter more fully explained. Control valves 30,32
are also arranged in interrupted series. The control
means 26 includes a flow control valve 34 which limits
the maximum amount of pressurized fluid being directed
from the second source 24 to the third work element
28. This assures that a controlled portion of the
total amount of the pressurized fluid from the second
source 24 is simultaneously deliverable to the second
and third work elements 16,28.
The first means 23 for transmitting the signal
25 includes a pressure actuated travel alarm switch 48
and a selector valve 50, which is activated by the
switch 48.
The fluid control system 10 has a pilot
actuating system 36 having a plurality of pilot
actuating valves 40,42,44 for actuation oE the control
valves 20,22,30,32, and a third source o~ ~luid
pressure 38. For clarit~, the Gonnecting lines between
the pilot actuating valves 40,42,44 and the associated
control valves 20,22,30,32 have been broken. In the
drawing, line ends with common letters are in fluid
communication with each other.
A brake valve 46 and the travel alarm switch
48 are in fluid communication with the track motor 14.
When the track motor 14 is activated, the brake valve
46 is shifted to pressurize cylinder 47 which releases
the track brakes 49, and at the same time activates the
travel alarm switch 48 and its associated alarm.
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Actuation of the travel alarm switch 48 transmits a
signal 25 to a selector valve 50, which shifts the
valve 50 to bring lines e and f into communication with
the actuating valve 40. With the selector valve 50 in
this position, actuating valve 40 is in communication
with control valve 32, and in response to shifting
valve 40, pressurized fluid is delivered from pump 24
via control valve 32 to the work element 16. Since the
pump 12 is supplying the work element 14, it cannot
simultaneously supply the work element 16. However, in
response to the signal which is generated by the travel
alarm switch 48, the pump 24 can supply the work
element 16 via selector valve 50 and control valve 32,
but the selector valve 50 is actuated only in response
to receiving the signal from the travel alarm switch,
which indicates that the work element 14 is actuated.
Industrial Applicability
The subject fluid control system 10 is
particularly useful for controlling operation of
various work elements 14,16,28 of an excavator-type
machine, such as a tree harvester. It should be
understood, however, that the system can be utilized on
other machines without departing from this invention.
In the pre~erred example, the pump 12 supplies
pressurized fluid to a track motor 14 via the control
valve 20. ~he track motor 14 propels the machine in a
preselected direction determined by the position of the
control valve 20. Actuation of the control valve 20 is
assisted by the pilot actuating system 36, including
the actuating valve 42.
Simultaneous actuation of the track motor 14
and the swing motor 16 solely by the pump 12 is not
possible since the track motor 14 has priority.
However, simultaneous operation of the swing motor 16
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is desirable and advantageous in order to position the
upper portion of the machine during travel of the
machine. To accomplish this function, swing motor 16
is activated via control valve 32, actuator valve 40,
and selector valve 50. A signal 25 is generated by the
travel alarm switch 48 in response to activation of the
track motor 14 and is transmitted to the selector valve
50 to shift the valve 50 and position lines e and f in
communication with the control valve 32. Shifting of
the actuating valve 40 actuates the control valve 32
and supplies fluid power to the swing motor 16.
With the system of this invention, it is also
possible to provide simultaneous power to the track
motor 14, the swing motor 16, and the work element 28.
To accomplish this, the actuating valve 44 is shifted
which in turn shifts the control valve 30 to provide
the work element 28 with pressurized fluid from the
pump 24. Under these conditions, the flow control
valve 34 limits the maximum volume of fluid available
to the work element 28.
Other aspects, objects and advantages of this
invention can be obtained from a study of the drawing,
the disclosure, and the appended claims.
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