Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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HYDRAULIC SYSTEM FO~ MATERIAL COMPACTING APPARATUS
_ . _
Field of the Invention
.
The present invention is concerned with improvements in
or relating to hydraulic systems for material compacting
apparatus, and especially but not exclusively, to such system~
for self-propelled refuse compacting vehicles.
Review of the Prior Art
Material compacting apparatus, and particularly refuse-
compacting vehicles are now a well-established part of many
large-size industrial material handling systems. Such a vehicle
usually consists of a truck mounting a compactor apparatus on its
chassis, and having at its front end a pair of controllable
lifting and tilting arms that are engaged by the operator with
a free-standing container. Thereafter the arms are lifted and
tilted to discharge the container contents into a compactor
hopper, and to return the container to its original position.
A compacting ram within the hopper is then operated either while
the truck is stationary or while it is moving to the next pick-up
point to compact the material into the space at the rear of the
hopper. When the hopper is sufficiently full a rear door is opened
and the ram operated to discharge the compacted contents. The
control and operating system for such a vehicle must be readily
operable by relatively unskilled personnel, also bearing in mind
that some operations are carried out while the truck is being
driven, and must permit foolproof control of powerful equipment
that can cause extensive damage if malfunction occurs. Although
I am aware that electrical-hydraulic ~ystems and mechanical-
hydraulic systems have
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previously been employed, to my knowledge an entirely hydraulic
system has not been proposed or used hitherto.
Definition of the Invention
It is therefore an object of the invention to provide an
entirely hydraulic control and operating system for material
compacting apparatus.
It is a more specific object to provide such a system for
refuse compacting vehicles.
In accordance with the present invention there is provided
a hydraulic control and operating system for material compacting
apparatus mounted on a self-propelled vehicle, wherein the
apparatus comprises:
a hopper for receiving the material, the hopper having an
inlet thereto for uncompacted material, an outlet therefrom for
compacted material, and a wall member against which the received
material is compacted,
a ram member mounted in the hopper for compacting movement
toward the wall member and opposite retracting movement away from
the wall member,
hydraulic ram motor means connected to the hopper and the
ram means and operative to move the ram means in the said opposite
compacting and retracting movements,
arm means for engagement with a container and for moving
the container to discharge the contents of the container into the
hopper,
hydraulic arm motor means for moving the said arms, and
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pump means for supplying operating liquid under
pressure to the hydraulic ram motor means and the hydraulic arm
motor means under control of the system,
the system comprising:
manually-operated arm motor valve means for controlling
the supply of operating liquid to the arm motor means,
ram motor valve means controlling the supply of
operating liquid to the ram motor means to cause either of the
said opposite movements of the ram means, and
ram relay valve means having an operating plunger
engaged by the ram member in nits fully retracted position, the
ram relay valve means when its plunger is so engaged permitting
supply of operating liquid under control of the said
manually-operated arm motor valve means for the said hydraulic
arm motor means, and when nits plunger is not so engaged
preventing supply of operating liquid under control of the said
manually-operating arm motor valve means to the said hydraulic
arm motor means so that the arms cannot be actuated unless the
ram member is in its fully retracted position.
Preferably the said arm means includes:-
fork means pivotally mounted on the arm means and for
engagement with a container to be lifted by the arm means,
hydraulic fork motor means connected between the arm
means and the fork means and for moving the fork means relative
5 to the arm means, and
manually-operated fork motor valve means for
controlling the supply of operating liquid to the fork motor
means,
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wherein the said arm motor valve means and fork motor
valve means comprise a single joystick type proportional valve
operable in a first direction for control of the arm motor means
and in a second direction transverse to the first direction for
control of the fork motor means,
and wherein the said ram relay valve means when its
plunger is not engaged by the ram member prevents supply of
operating liquid to the joystick valve so that both the arm
motor valve means and the fork motor valve means are disabled.
Description of the Drawings
A hydraulic system for a refuse compacting vehicle that
is a particular preferred embodiment of the invention will now
be described, by way of example, with reference to the
accompanying diagrammatic drawing wherein:
FIGURE 1 is a side elevation of a typical vehicle
employing the system, and
FIGUR~ 2 is a schematic diagram of the hydraulic system.
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Description of the Preferred Embodiments
Since the speci~ic structure of the vehicle is not
part of this invention the construction as illustrated by Figure
1 has been considerably simplified to omit inessential details~
Thus, the vehicle is shown as consisting of a chassis 10 on which
is mounted a driver's cab 12 and a hopper container 14. The
hopper is provided with a top door 16 pivoted at 18 and having
connecting operating linkages 19, each with a cam follower 20, this
door closing a respective loading opening. A rear door 22 i8
pivoted at 24 and closes a respective discharge opening. The door
22 is controlled in its pivoting opening and closing movement by a
pair of hydraulic piston and cylinder motors 26 (only one is seen
in Figure 1). A compacting ram 28 as shown in broken lines i8
mounted within the hopper for movement from the front to the
rear, and vice versa, under the control of a high-extension, multi-
cylinder hydraulic motor 30. A bifurcated arm structure 32 is
pivoted in front of the hopper 14 and reaches over the cab 12 in
the travelling and container-engaging positions, the front ends of
the arm structure carrying a fork structure 36 pivoted thereto at
38. Novement of the arm structure relative to the chassis is
controlled by a pair of hydraulic motors 40, while the movement
of the fork structure 36 relative to the arm structure 32 is
controlled by a pair of hydraulic motors 42~ The door 16 is
opened automatically in known manner upon movement of the arm
structure 32 to a container discharge position above the hopper~
when cam fo71Owers are engaged by respective cams 43 on the
arm structure thereby causing operation of the linkage~ 19 to
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open the door. The door closes again automatically upon return
movement of the arm structure.
The mode of operation of such a vehicle is now
extremely well known. The driver engages the fork structure 36
with a free-standing refuse container, and then operates the
motors 40 to lift and tilt the container until it can be emptied
into the front end of the hopper, the cams 43 and linkages 19
opening the door 16 before the container reaches its tilted
emptying position. The container is then returned to the ground
while the door 16 closes, the fork structure 36 is disengaged
therefrom, and returned to an elevated travelling position, and
the vehicle is driven to the next pick-up location while the ram
motor 30 is operated to compact the waste to the rear of the
hopper against the door 20. Side shields 44 and 46 are provided
to prevent spilling of waste as the container is emptied. A side
inspection hatch 48 is also provided.
Referring now to Figure 2 the truck engine 50 is
employed in conventional manner to drive a two stage hydraulic
pump; the reason for employing such a pump will be explained
below. The pump is operated either in a single stage low
delivery mode, or a two stage high delivery mode under control
of a manual switch 53 located in the cab 120 This pump draws
operating liquid from a resérvoir 54 via a strainer 56 and shut
off valve 58 and delivers it under pressure to the circuit via a
check valve 60 that sets the minimum pressure for the system, to
ensure that there is ~ufficient pressure for operation of the
valves of the system; in a typical ~ystem this valve operates
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at about 7 Kg/sq.cm. ~100 p.s.i.). A pressure relief valve 61
operative at about 21 Kg/sq.cm. (300 p.s.i.) ensures that this
system operating pressure cannot rise above its present value, the
excess liquid being returned to the reservoir. A second pressure
relief valve 62 ensures tha~ the pressure of the operating
liquid supplied to the various motors cannot rise above a safe
value, e.g. about 123 Kg/sq.cm. (1,750 p.s.i.). The excess liquid
from the relief valves 61 and ~2 passes to the reservoir via a
filter 64, shut-off valve 66 and strainer 68.
The system comprises a plurality of manually operated
valves disposed for easy access by the driver, and a plurality
of relay valves arranged to provide the desired sequence of
operations automatically. A proportional hydraulic pressure
reducing valve 70 is provided and is positioned by the driver to
lS give the desired liquid flow, and therefore the corresponding
motor operating speed, to the pilot valves which it supplies,
namely valves 72 and 74, controlling respectively the motors
40 and 42. The valve 70 is of the "joystick" type so that the
two sets of motors can be operated simultaneously and at different
speeds. A manually-operated directional valve 76 is used to
control pilot valve 78 which in turn controls tailgate motors 26
A manual "emergency stop" valve 80 when operated by-passes the
entire hydraulic control system and returns the liquid directly
to the reservoir 54 to stop all the motors in the positions ifi
which they stand when the stop valve is actuatedO
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The ram is usually ope~ated during the collection of
refuse while the vehicle is bein~ drl~en and it~ operation i~
therefore as automatic as po~sible. A two stage pump 52 is
used and in a typical embodiment the pump will supply either 55
or 260 litres per minute at a shaft speed of 1200 r.p~m. The
higher delivery rate is normally used while the vehicle is
standing for the fastest possible operation, while the lower
rate is used at other times, when much slower operation is
completely adequate; this avoids the overheating and need for
auxiliary coolers that might otherwise occur if the pump must
always operate a a con~tant high rate. The pump may be left
connected to the truck engine at all times and power is there-
fore always available for operation of the system: this is not
usually possible with a system employing a mechanical power
take-off. As the vehicle moves away from the ~ite of the pick-
up,manual ram control valve 82 is actuated and cause~ flow of
liquid to pilot valve 84 to shift this valve and also to enable
this valve to feed liquid to a spring-centered ram pilot valve
86, which in turn feeds liqu~d to the ram motor 30 causing
extension of the cylinder and movement of the ram toward the rear
of the hopper. In its foremost position the ram 28 is in
contact with the plunger of a directional control valve 88; after
a small movement of the ram (e.g. about 2-3 cm) the ram disengages
from the valve plunger, and that valve now operates to maintain
the liquid flow to the valve~ 84 and 86. Moreover, the joystick
~alve 70 is now by-pas~ed and cannot cause operation of the arm
motor~, even if manipulated, 80 that tho~e motor~ are disabled.
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Pilot valve 84 i~ of the type in wh,.ch the spool is
detented in both directions so that it will re.main in the control
position in which it was last placed until positi.vely moved
therefrom; the ram will therefore continue its compacting
movement to the rear. When the deposited material is compacted
as tightly as possible the ram will come to a stop and pressure
will now build up in the Yystem. This pressure is applied to a
sequencing valve 90 which previously ha~ been set in the position
illustrated in Figure 2, in which it connects one side of a shuttle
valve 92 back to the reservoir, the other side of the ~huttle
valve being connected to the ram control valve 82. When the ram
motor pressure applied to the valve 90 has risen to a suitable
value the shuttle valve 92 is shifted and the high pressure is
applied to the v.alve 84 to shift it, whereupon pilot valve is also
~hifted and the motor 30 operates to retract the ram. The detent
of valve 84 holds it in the "ram retract" position despite the
loss of the elevated pressure through the shuttle valve 92.
Upon return of the ram to the fully retracted position
it engages the plunger of valve 88, which is then operative to
restore flow to the joystick valve 70 and diverts flow from the
valve 84 the flow to pilot valve 86 then stops and this valve
centres under control cf its centering spring~ It is possible
for the operator at any ti~e to reverse the ram movement by
reverse manual operation of the valve 82~ whereupon an excess
of pressure goes to the shuttle valve 92~ which transmits thi~
pressure as an operating pressure to the pilot valve 84; the valve
shifts as described above and shifts valve 86 to retract the ram~
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The function of the shuttle val~e 92 is therefore highl~ important
in permitting the control of the ram operation both automatically
and manually, by accepting an excess pressure ~rom the two
possible sources and applying this excess pressure as a control
pressure to the pilot valve 84, without interference of the two
sources with one another and therefore withtheir Reparate function~.
The circuit is provided in known manner at appropriate locations
with relief valves 94, 96 and 98, which are ~et at the pre~sures
neces~ary to protect their associated component~, and with check
va~ves 100, 102 and 104 to prevent reverse liquid flows. A pilot
operated unloading valve 106 is operative when the pressure of
the liquid supplied to the motor 30 drop3 upon the ram retraction
and permits fast dumping of the liquid in the ram motor 30 back
to the reservoir 54~ increasing the speed at which the ram can
be retracted~
It will be seen therefore that we have provided an
entirely hydraulic control and operating ~ystem that provides
the desired manual and automatic control, without the need for
electrical relays and/or mechanical link connections between valve~.
Although the system has been de~cribed in relation to a truck
mounted arrangement, it will be apparent to those skilled in the
art that it is equally applicable to a stationary system, such
as would be required by an apartment building or a shopping centre,
in ~hich for example the ram operation is initiated at predetermined
times by a timing device, ~ith the option of manual control when
required.
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It is found in practice that a completely hydraulic
system with a permanently operating pump as described permits
much faster system operation than prior systems using a mechanical
power take off. For example, with such a prior system the operator
must stop the vehicle before the container, engage the p.t.o.
and lower the arm structure, disengage the p.t.o. and move the
vehicle to engage the arms with the container, engage the p.t.o.
and empty the container, and so on, it not being possible to move
both the vehicle and the arm structure simultaneously. With the
system of this invention the operator is able to adjust the positions
of the arm and fork ~tructures while approaching the container,
and can return them to their travelling position while leavinq the
pick up site, minimizing the time required for each pick up.
Among the advantageY of a completely hydraulic system is
its relative freedom ~rom service problems as compared with
mechanical or electrical systems, bearing in mind that these
systems are expected to operate under extremely arduous conditions.
For example, it is found wit~ mechanical system~ that the moving
parts have a tendency to bind after a while~ and to become frozen
20 ~ during cold weather, while with electrical systems ~here is a
tendency toward failure3 due to the common electrical fault~,
such a-~ broken wire~ and corroded con nection~.
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