U.S. patent number 3,872,670 [Application Number 05/356,362] was granted by the patent office on 1975-03-25 for selectively actuatable shock absorbing system for an implement control circuit.
This patent grant is currently assigned to Caterpillar Tractor Co.. Invention is credited to Joseph E. Dezelan, John A. Junck, Walter I. Nelson.
United States Patent |
3,872,670 |
Dezelan , et al. |
March 25, 1975 |
SELECTIVELY ACTUATABLE SHOCK ABSORBING SYSTEM FOR AN IMPLEMENT
CONTROL CIRCUIT
Abstract
Hydraulic control system for holding a work implement in a fixed
position, said system including selectively operative shock
absorbing means for negating any large force experienced by the
implement on contact with an immovable object.
Inventors: |
Dezelan; Joseph E. (Joliet,
IL), Junck; John A. (Joliet, IL), Nelson; Walter I.
(Decatur, IL) |
Assignee: |
Caterpillar Tractor Co.
(Peoria, IL)
|
Family
ID: |
23401159 |
Appl.
No.: |
05/356,362 |
Filed: |
May 2, 1973 |
Current U.S.
Class: |
60/413; 60/484;
60/469 |
Current CPC
Class: |
F15B
13/01 (20130101); E02F 9/2217 (20130101); F15B
1/02 (20130101); E02F 9/2207 (20130101) |
Current International
Class: |
E02F
9/22 (20060101); F15B 1/00 (20060101); F15B
13/01 (20060101); F15B 1/02 (20060101); F15B
13/00 (20060101); F15b 001/02 () |
Field of
Search: |
;60/413,414,416,469,466
;91/420 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Schwadron; Martin P.
Assistant Examiner: Burks, Sr.; H.
Attorney, Agent or Firm: Phillips, Moore, Weissenberger,
Lempio & Strabala
Claims
What is claimed is:
1. A hydraulic system for selectively holding an implement or the
like in a fixed position and for selectively providing shock
absorbing means for the implement comprising:
a hydraulic motor;
a source of fluid pressure;
first control valve means comprising lock valve means disposed in a
motor control circuit between said source of fluid pressure and
said hydraulic motor for selectively directing said fluid to and
from said motor; and
shock absorbing means comprising fluid accumulator means and
control means including second control valve means independent of
said first control valve means including pilot operated lock valve
means disposed between said fluid accumulator means and said
hydraulic motor and operated by a pilot control circuit independent
of said motor control circuit and including a two-position selector
valve for selectively communicating said fluid accumulator means
with said motor.
2. The hydraulic system of claim 1 wherein said fluid accumulator
means comprises a gas charged accumulator.
3. The hydraulic system of claim 1 wherein said lock valve means of
said selector valve means comprises:
passage means connecting said fluid accumulator means with said
motor;
check valve means disposed in said passage means to normally
isolate said fluid accumulator means from said motor;
means for unseating said check valve means to provide communication
between said accumulator means and said motor.
4. The hydraulic system of claim 1 wherein said means for unseating
said check valve means comprises:
a pressure responsive piston; and
said second valve means is operatively connected for directing
fluid from said source to said piston.
5. The hydraulic system of claim 4 including a source of electrical
power and manually operable switch means for selectively activating
said solenoids.
6. The hydraulic system of claim 1 including a second hydraulic
motor;
a second accumulator for connection to said second motor,
said pilot-operated lock valve means includes a second lock valve
disposed between said second hydraulic motor and said second
accumulator for controlling communication between said second motor
and said second accumulator; and
said second control valve means includes a pair of
solenoid-operated two-position valves.
Description
BACKGROUND OF THE INVENTION
Many earth working machines employ hydraulic jacks for controlling
work implements. The jacks are usually actuated by spool-type
control valves which have a tendency to leak causing the jacks to
drift. Although slight drifting is not detrimental to the operation
of most earth working machines, it can be a problem in a grading
machine where the operator must accurately hold the grader blade in
a fixed position for relatively long periods of time to produce a
level road surface. In order to achieve such blade accuracy lock
valves are commonly included in the hydraulic circuitry for the
blade lift jacks. Such lock valves are positioned between the
control valve and the jacks and function to block fluid flow from
the jacks when the control valve is in the neutral position. With
the fluid flow blocked, the jacks are prevented from drifting and
the grader blade is held in a fixed position.
This rigid blade positioning is highly desirable if the motor
grader is being used for final finish grading and the machine is
traveling at relatively slow speeds. During rough grading work,
however, the motor grader travels at relatively high speeds and the
grader blade frequently encounters hard immovable objects, such as
large rocks and the like which are embedded in the soil. Because of
the lock valve, however, the blade is prevented from moving and
impact with such objects frequently causes damage, both to the
blade and related components. Therefore, while it is desirable for
the blade to be rigidly held during finish grading operations, it
is equally desirable that the blade be permitted to move upon
impact during rough grading operations.
Examples of prior art related to the present invention include U.S.
Pat. No. 3,543,647, issued Dec. 1, 1970 to Hall et al. and U.S.
Pat. No. 3,587,399, issued June 28, 1971 to Parquet et al. These
patents generally disclose hydraulic systems having lock valves
provided with pilot pressure actuated pistons for unseating spring
biased check valves. U.S. Pat. No. 3,213,762, issued Oct. 26, 1965
to DuBuf is of interest in showing a check valve assembly for
hydraulic systems having high inertia.
While the above patent art does disclose pilot operated check valve
assemblies, none of the patents cited show such an assembly
including shock absorbing means.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide means
for overcoming the above deficiencies of the prior art.
Another object of the present invention is to provide a hydraulic
control system for holding a work implement in a fixed
position.
A further object of the present invention is to provide shock
absorbing means for use in a hydraulic control circuit for negating
large forces experienced by the work implement on contact with
immovable objects.
Still another object of the present invention is to provide
selectively actuatable shock absorbing means including fluid
accumulator means for connecting the accumulator means with the
implement lift jacks.
A still further object of the present invention is to provide lock
valve means having pilot pressure actuated pistons for unseating
the valve checks.
In accordance with the present invention there is provided a
hydraulic implement control circuit in operative combination with
selectively responsive shock absorbing means. The shock absorbing
system functions to negate any large force experienced by the
implement upon contact with an immovable object.
BRIEF DESCRIPTION OF THE DRAWINGS
Other and further objects, features and advantages of the present
invention will be apparent in the following description taken in
conjunction with the accompanying drawings:
FIG. 1 is a schematic diagram of a hydraulic control system
embodying the present invention.
FIG. 2 is a schematic illustration of an alternate embodiment of
the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 1, there is illustrated a hydraulic control
system embodying the principals of the present invention. The
system includes shock absorbing means, generally indicated by the
numeral 10, in combination with a hydraulic control circuit 11 for
a pair of lift jacks 12 and 13 which may be employed for
controlling a motor grader blade or the like. The system includes a
pump 15 which draws fluid from a tank 16 to provide fluid pressure
to a pair of control valves 18 via conduits 20 and 21. The control
valves 18 may be of any suitable well known construction. Fluid
exhausted from the control valves 18 is returned to the tank 16 by
conduits 22 and 23. A relief valve 24 is interconnected between the
output of the pump 15 and the tank 16 to relieve excessive pressure
in the hydraulic system.
As the hydraulic circuits for each of the control valves 18 are
identical, the same numbers are used to identify similar components
thereof. The control valves 18 direct fluid pressure to and from a
pair of lock valves 26 via conduits 28 and 29. The lock valves may
be of any suitable construction known in the art. The lock valves
26 permit fluid flow to and from the rod and heads ends of the lift
jacks 12 and 13 via conduits 32 and 33 respectively.
The shock absorbing system 10 includes a pair of fluid accumulators
48 and 49 and a lock valve 34 including control means to
selectively connect the accumulators to the jacks 12 and 13. The
lock valve 34 includes a valve housing 36 provided with an
elongated cylindrical bore 38. A first pair of laterally spaced
ports 40 and 41 connect opposite ends of the bore 38 with the head
ends of the lift jacks 12 and 13 via conduits 42 and 43
respectively. A second pair of ports 44 and 45, disposed
intermediate the first ports 40 and 41, connect the bore 38 with
shock absorbing means such as a pair of gas charged fluid
accumulators 48 and 49 via conduits 50 and 51 respectively.
The lock valve 34 further includes a pair of identical spring
biased ball check valve assemblies 52 and 53 mounted in the valve
bore 38. Check valve assembly 52 is interposed ports 40 and 44 to
normally block fluid flow from the head end of the jack 12 to the
accumulator 48 via conduits 42 and 50. Check valve assembly 53 is
interposed ports 41 and 45 to normally block fluid flow from the
jack 13 to the accumulator 49 via conduits 43 and 51.
A pair of pistons 56 and 57 are slidably disposed in the bore 38
between the check valve assemblies 52 and 53. The pistons have
opposing radial faces provided with abutting protuberances 58 which
serve to separate the pistons and provide a variable fluid chamber
59 therebetween. The outer ends of the pistons 56 and 57 are
provided with axial plungers 60 and 61 which engage and unseat the
check valves 52 and 53 when the chamber 59 is pressurized
sufficiently to overcome the fluid pressure and spring forces
acting to seat the valves.
A conduit 64 communicates fluid pressure between the chamber 59 and
a solenoid operated, two position valve 66. Pressurized fluid is
communicated to the valve 66 from the pump 15 through conduit 68
and returned to the tank through conduit 69. The solenoid operated
valve 66 is selectively actuated through normal closure by the
operator of a manually operated switch 70 which communicates
electrical current from a battery 72 to the valve solenoid through
a lead 74.
In operation, closure of the switch 70 shifts the solenoid operated
valve 66 to communicate fluid pressure from the pump 15 to the
chamber 59 via conduits 68 and 64. When the chamber 59 is
sufficiently pressurized, the pistons 56 and 57 are moved outwardly
and the axial plungers 60 and 61 engage and unseat the ball checks
of valve assemblies 52 and 53 respectively. The unseating of the
valve assemblies 52 and 53 permits communication of ports 40 and 41
with ports 44 and 45 respectively so that the head end of jack 12
is in communication with accumulator 48 via conduits 50 and 42 and
the head end of jack 13 is in communication with accumulator 49 via
conduits 51 and 43. Consequently, if a large external force F is
experienced on the rod end of one or both of the jacks 12 and 13,
such as occurs when a grader blade connected to the jacks hits an
object, the energy from the impact is absorbed by one or both of
the accumulators 48 and 49, and the jacks 12 and 13 are permitted
to retract. After such an impact, the energy stored in the
accumulators 48 and 49 returns the jacks 12 and 13 to their former
positions.
When the switch 70 is open, fluid pressure from the pump 15 is
blocked by the valve 66 and the chamber 59 is open to the tank 16
via conduits 64 and 69. Under these conditions the spring biased
check valves 52 and 53 will be seated and escape of fluid from the
jacks 12 and 13 will be prevented. Thus, with the switch 70 open,
the hydraulic system functions in a conventional manner and may be
employed for final finish grading operations.
FIG. 2 illustrates an alternate embodiment of the present
invention, wherein identical elements are identified by the same
numerals and equivalent elements by the number primed. This
embodiment differs from FIG. 1 primarily in that the lock valve has
been replaced by a pair of solenoid operated selector valves 75 and
76 which are actuated through closure of a switch 77 which
communicates electrical current from a battery 78 to the valve
solenoids through a lead 79.
Thus, there is provided a hydraulic control system for positioning
a work implement, having means to selectively bring shock absorbing
means into the circuit.
* * * * *