HYDRAULIC SYSTEM FOR A PLOWING AND MATERIAL SPREADING EQUIPMENT

SYSTEME HYDRAULIQUE POUR EQUIPEMENT DE DENEIGEMENT ET D'EPANDAGE

English Abstract

A hydraulic system for operating equipment for removing snow and/or ice from surfaces having a plow, and a spreader for spreading traction enhancing materials onto the surfaces comprises a fixed displacement pump, a priority valve for receiving all of the hydraulic fluid from the pump and directing it to a load sensitive spreader valve and a plow valve. The priority valve is mechanically biased to direct the hydraulic fluid primarily to the spreader valve. The pressure from the fluid directed to the spreader valve is used to oppose the mechanical bias while the load pressure from the spreader valve is used to augment the mechanical bias, such that the spreader valve receives the amount of hydraulic fluid required for its operation. The system further includes an orifice connected to a load sensing line in the spreader valve to bleed fluid from the line. The spreader may include a conveyor and/or an auger and a spinner for spreading materials, as well as a dispenser for liquid materials. The metering devices for operating the components in the spreader may be solenoid or mechanically operated; the metering devices for operating the plow may be solenoid, air, hydraulic or mechanically operated.

French Abstract

Un système hydraulique pour faire fonctionner de l'équipement de déneigement et/ou d'enlèvement de la glace de surfaces, possédant un chasse-neige, et un dispositif d'épandage pour épandre le matériel d'amélioration de la traction sur les surfaces, comprend une pompe volumétrique fixe, une vanne de priorité pour recevoir tout le liquide hydraulique qui provient de la pompe et l'acheminer à la vanne du dispositif d'épandage sensible à la charge et à la vanne du chasse-neige. La vanne de priorité est mécaniquement polarisée pour diriger le liquide hydraulique principalement vers la vanne du dispositif d'épandage. La pression du liquide dirigé vers la vanne du dispositif d'épandage est utilisée pour opposer la polarisation mécanique, alors que la pression de la charge du dispositif d'épandage est utilisée pour augmenter la polarisation mécanique, de sorte que la vanne du dispositif d'épandage reçoit la quantité de liquide hydraulique nécessaire à son fonctionnement. Le système comprend également un orifice connecté à une conduite de détection de charge dans la vanne du dispositif d'épandage pour purger le liquide de la conduite. Le dispositif d'épandage peut comprendre un transporteur et/ou une vis sans fin et une tournette pour le matériel d'épandage, ainsi qu'un distributeur pour le matériel liquide. Les compteurs servant au fonctionnement des composants dans le dispositif d'épandage peuvent fonctionner grâce à un solénoïde ou fonctionner mécaniquement; les compteurs servant au fonctionnement du chasse-neige peuvent fonctionner grâce à un solénoïde, ou à l'air ou à l'huile hydraulique, ou encore fonctionner mécaniquement.

Claims

9
What is claimed is:
1. In equipment for removing snow and ice from surfaces having a plow and a
spreader for spreading traction enhancing materials onto the surfaces, a
hydraulic
system for operating the spreader and the plow comprising:
- reservoir means for hydraulic fluid;
- fixed displacement pump means for providing hydraulic fluid from the
reservoir;
- priority valve means having an inlet port for receiving hydraulic fluid from
the
pump means, a first outlet port and a second outlet port, whereby the priority
valve means is mechanically biased to direct the hydraulic fluid from the
inlet
port primarily to the first outlet port;
- spreader valve means having an inlet port coupled to the priority valve
means
first outlet port and means for controlling fluid flow through the spreader
valve for operating the spreader;
- plow valve means having an inlet port coupled to the priority valve means
second outlet port and means for controlling fluid flow through the plow valve
means for operating the plow;
- means for transferring pressure from the priority valve means first outlet
port
to the priority valve means to oppose the mechanical bias thereby directing
fluid flow to the second outlet port;
- means for transferring load pressure from the spreader valve means to the
priority valve means through a load pressure line to augment the mechanical
bias, such that the amount of hydraulic fluid directed from the priority valve

10
means first outlet port is proportional to the load pressure from the spreader
valve means; and
- means for bleeding fluid to the reservoir means from the load pressure
transferring means.
2. A hydraulic system as claimed in claim 1 wherein the means for bleeding
hydraulic fluid comprises an orifice connected between the load pressure line
and the reservoir means.
3. A hydraulic system as claimed in claim 2 wherein the orifice is located in
the
spreader valve means.
4. A hydraulic system as claimed in claim 1 which further includes a relief
valve
connected between the priority valve means and the reservoir means to relieve
the pressure in the load pressure transferring means.
5. A hydraulic system as claimed in claim 1 wherein the means for controlling
the fluid flow through the spreader valve means is a solenoid operated
metering device.
6. A hydraulic system as claimed in claim 1 wherein the means for controlling
the fluid flow through the spreader valve means is a mechanically operated
metering device.
7. A hydraulic system as claimed in claim 1 wherein the spreader includes a
conveyor, an auger and a spinner for the materials.
8. A hydraulic system as claimed in claim 1 wherein the spreader includes a
conveyor or auger and a spinner for the materials.

11
9. A hydraulic system as claimed in claims 7 or 8 wherein the spreader
includes a
liquid dispensing device.

Description

CA 02390186 2002-07-02
1
HYDRAULIC SYSTEM FOR PLOWING AND MATERIAL SPREADING
EQUIPMENT
Field of the Invention
The invention relates generally to equipment for removing snow and/or ice
from roadways, and more particularly to a hydraulic system for controlling the
equipment spreader and plow.
Background of the Invention
The operation of equipment used for plowing or scraping snow and/or ice
from roads, airport runways and similar surfaces and the spreading of traction
enhancing material such as sand and/or salt requires the installation of a
hydraulic
system that supplies power to operate the spreader and plow equipment. The
usual
installation includes a single gear pump that pushes hydraulic fluid through
an open
center valve with a power beyond connection, which is used to operate the plow
functions. The power beyond is connected to the pressure inlet of the spreader
valve,
from where it returns to a hydraulic fluid tank or reservoir, or is partially
routed to the
spreader's hydraulic motors. The principal problem of this circuit is the
stoppage of
2o the spreader when any plow function is operated. Other solutions have been
used to
remedy this problem.
Tandem pumps may be used in two completely separate hydraulic circuits.
One pump supplies the plow hydraulic functions, the other one supplies the
spreader
only. Simultaneous operation is rendered possible for both the plow and the
spreader,
but several major inconveniences remain. The system is more expensive, more
complicated, requires a larger hydraulic fluid reservoir and consumes more
energy.
Another solution is the use of a variable displacement piston pump that is
3o usually controlled by sensing the load. The load sensing pump works in
conjunction
with closed center valves that share a common pressure supply, which is the
pump.
This constitutes a normal load sensing circuit, with all its usual benefits.
The main

CA 02390186 2002-07-02
problem associated with this solution is the very high cost of load sensing
valves and
pumps.
Canadian Patent 1,060,757 which issued on August 21, 1979 to Larson et al is
an example of various types of hydraulic circuits based on a fixed
displacement pump,
a variable displacement pump or a load sensing pump. In this patent, the
circuits are
used in power steering systems, which selectively control the flow of fluid
toa
steering motor and an auxiliary device through the use of a priority valve.
1o Therefore, there is a need for a hydraulic system that provides hydraulic
fluid
to the spreader on a priority basis in spreader/plow equipment.
Summary of the Invention
The invention is directed to a hydraulic system for operating equipment for
Is removing snow and/or ice from surfaces having a plow, and a spreader for
spreading
traction enhancing materials onto the surfaces. The hydraulic system comprises
a
reservoir for hydraulic fluid, a fixed displacement pump for providing
hydraulic fluid
from the reservoir, a priority valve having an inlet port for receiving
hydraulic fluid
from the pump, a first outlet port and a second outlet port, whereby the
priority valve
2o is mechanically biased to direct the hydraulic fluid from the inlet port
primarily to the
first outlet port. The system further includes a spreader valve having an
inlet port
coupled to the priority valve first outlet port and one or more metering
device for
controlling fluid flow through the spreader valve for operating the spreader,
and a
plow valve having an inlet port coupled to the priority valve second outlet
port and a
z5 metering device for controlling fluid flow through the plow valve for
operating the
plow. In addition, the system has means for transferring the pressure from the
priority
valve first outlet port to the priority valve to oppose the mechanical bias
thereby
directing fluid flow to the second outlet port, means for transfernng load
pressure
from the spreader valve to the priority valve through a load pressure line to
augment
3o the mechanical bias, such that the amount of hydraulic fluid directed from
the priority
valve first outlet port is proportional to the load pressure from the spreader
valve, and
means for bleeding fluid to the reservoir from the load pressure transferring
means.

CA 02390186 2002-07-02
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In accordance with another aspect of the invention, an orifice is connected
between the load pressure line and the reservoir to bleed fluid from the load
pressure
transferring means. The orifice may be located in the spreader valve.
With regard to a further aspect of the invention, the system may include a
relief valve connected between the priority valve and the reservoir to relieve
the
pressure in the load sensing line. The relief valve may be located in the
priority valve.
1o In accordance with another aspect of the invention, the metering device for
controlling the fluid flow through the spreader valve may be solenoid operated
or
mechanically operated.
With respect to another aspect of the invention, the spreader may include a
conveyor and/or auger and a spinner for spreading materials, as well as a
liquid
material dispenser.
Other aspects and advantages of the invention, as well as the structure and
operation of various embodiments of the invention, will become apparent to
those
ordinarily skilled in the art upon review of the following description of the
invention
in conjunction with the accompanying drawings.
Brief Description of the Drawings
The invention will be described with reference to the accompanying drawings,
wherein:
Figure 1 illustrates the hydraulic system in accordance with the present
invention;
Figure 2 is a schematic of a priority valve used with the present invention;
and
Figure 3 is schematic of an alternate spreader valve.
Detailed Description of the Invention
The hydraulic system in accordance with the present invention is illustrated
in

CA 02390186 2002-07-02
4
figure 1. A fixed displacement pump 1 pumps hydraulic fluid or oil at a
constant flow
and variable pressure from the reservoir 2 into the inlet port P3 of a
priority valve 3
where the flow is divided between the priority outlet port CF and the excess
flow port
EF. The priority outlet port CF is coupled to the inlet port P4 of a load
sensing
spreader valve 4 by line 6 while the excess flow port is coupled to the inlet
port P5 of
an open-centred plow valve S by line 7. For purposes of illustration, the plow
valve S
is shown as a conventional three-position, four way valve. By way of example,
the
load sensing spreader valve 4 is shown as having a first and a second branch
with
metering devices 41 and 42. Metering device controls fluid flow to motor for a
1 o material transporting device such as a conveyor, an auger or a combination
of both,
through outlet port P41, while metering device 42 controls fluid flow to a
spinner
motor through outlet port P42. Valve 4 further includes shuttle valves 43 and
44 such
that the highest pressure at the outlets of the metering devices 41 and 42 is
transferred
to a load sensing port LS4. Though valve 4 has been shown as having two
branches,
it may have further branches such as for a dispenser of liquid material.
The spreader valve 4 provides a pressure signal from the load sensing port
LS4 through a load sensing line 8 to the priority valve 3 load sensing inlet
port LS3.
The amount of fluid delivered to the spreader valve 4 by the priority valve 3
will
2o depend on the pressure signal received at the load sensing port LS3 from
the spreader
valve 4. The amount of fluid directed to the spreader valve 4 is directly
proportional
to the fluid pressure at the outlet of the spreader valve 4. In this way, the
priority
valve 3 meters the exact amount of fluid required for the operation of the
spreader.
Any pressure or flow changes in the excess flow line 7 have no influence on
the
metering towards the outlet port CF. The correct sizing of orifices in the
hydraulic
circuit provide for a damping effect, thus eliminating any sudden peaks in the
system
that might otherwise result in 'jerky' operation.
The hydraulic circuit may further include a relief valve 31 in the load
sensing
line 8 that limits the pressure in the spreader valve 4 circuit. The relief
valve 31 may
be incorporated into the priority valve 3 as shown in figure l, or it may be a
separate
component.

CA 02390186 2005-04-19
S
A bypass line 9 with an orifice 10 between the load sensing port LS3 and a
drain port T3 is provided to eliminate any possibility of leakage oil through
the
spreader valve 4 metering devices 41 and 42 building up pressure when the
spreader
valve 4 is in the OFF position. By-pass line 9 permits the use of spreader
valves 4 that
have no internal bleed-off for the fluid in the load-sensing line 8, which
would
otherwise be trapped in the load sensing line 8, maintaining higher than
necessary
pressure in the line between the pump 1 and the priority valve 3. Examples of
spreader valves 4 that do not have bleed-off are the Vickers~ ICSV3000, and
the
Danfoss~ 2FFC 12 or FFLC 12 valves. A by-pass line may be incorporated in the
design of the spreader valve itself such as in the 800 VALACE-2LS or in the
800
VALACE-3LS. Figure 3 is a schematic of such a valve 40 wherein orifice 45 is
connected between the load sensing line 8 and a drain port T4 internally in
the valve
40.
1 S Proper sizing of the pump 1 assures that, though the spreader valve is
operated
on a priority basis, there is sufficient excess hydraulic fluid for the
operation of the
plow valve 5.
The advantages of the above hydraulic circuit are numerous. A single fixed
displacement pump is the most economical power source for hydraulic systems.
The
use of standard open center valves for the plow functions is another
economical
advantage. The load sensing priority valve supplies only the oil required for
the
operation of the spreader, with no excess oil flowing to the reservoir. The
priority
valve may incorporate a relief valve, which permits the elimination of the
relief valve
in the spreader valve. The complete circuit is simple and affordable.
Many makes and models of priority valves exist on the market. For instance,
the Eaton~ load sensing priority valve comes in VLC, VLE and VLH Models. The
Danfoss~ Models OLS40 and OLS80 are priority valves without relief valves,
whereas Model OLS 160 has a relief valve incorporated. A schematic of the
valve 23
is illustrated in figure 2, which will be used to describe the operation of
valve 23 in the
hydraulic circuit 20 in accordance with the present invention which includes
the

CA 02390186 2002-07-02
6
fixed displacement pump 21, the spreader load sensitive valve 24 and the plow
valve
25.
The priority valve 23 is a pressure control valve that maintains priority
pressure to the closed center spreader valve 24. With the spreader valve 24
OFF, flow
through it is blocked and all flow through the priority valve 23 is directed
out the EF-
port to the plow control valve 25.
With the engine off, the spool 232 is pushed to the right by the spring 233.
The passage to the EF-port is blocked while the passage to the CRport is open
causing the fluid to flow through the plow valve 25.
When the pump 21 is first started, all pump flow is routed to the spreader
valve
24, which blocks the flow. With the flow blocked, the pressure increases. Pump
21
inlet pressure is supplied through the pilot orifice 234 to the right end of
the spool.
232. This causes the priority valve spool 232 to shift against the spring 233
and open
the EF-port. As long as the spreader valve 24 is OFF, just enough pressure is
maintained at the spreader valve 24 to keep the priority valve spool 232
shifted to the
left.
The operating pressure in the plow valve 25 circuit has no effect on the
operation of the priority valve 23. With the plow valve 25 in relief, the
priority valve
23 will not shift until the spreader valve 24 is activated.
When the spreader is working normally, load~ensing pressure from the
spreader valve 24 flows through the orifice LS-port LS23 in the priority valve
23.
The load-sensing pressure plus the spring 233 force the spool 232 to move to
the right
against the pilot pressure on the right end of the spool 232. This restricts
flow to the
plow through the EF-port while the CF-port is opened to the spreader valve 24.
The load-sensing circuit LS24/2$/LS23 is a control circuit that routes
spreader
pressure to the spring 233 side of the priority valve spool 232. It allows the
priority

CA 02390186 2002-07-02
valve spool 232 to sense the pressure required by the spreader through the
spreader
valve 24 under varying conditions.
During normal material spreading operation, oil is metered into the load-
s sensing circuit through an orifice in the spreader valve 24. The priority
valve 23
supplies just enough oil to the spreader valve 24 to satisfy its needs and
evacuates the
excess to the plow circuit EF/27/P25/25.
To limit the pressure in the spreader circuit CF/26/P24/24, a relief system
231
to may be built into the priority valve 23 or added as a separate component as
illustrated
in figure 2. When the conveyor jams, pressure in the spreader circuit
CF/26/P24/24
increases. This pressure is sensed at the LS-port LS23. When the pressure
increases
enough to push poppet 235 off of its seat, oil in the load-sensing circuit
LS24/28/LS23 flows to return through the T-port T23. Load sensing pressure is
is limited to the pressure setting of the relief valve 231.
Pressure to the spreader valve 24 (pilot pressure), which is sensed at the
right
end of the priority valve spool 232, continues to increase until it can move
the spool
232 to the left against the load-sensing pressure plus the spring 233 force.
At this
2o time all oil flows out of the EF-port to the plow circuit EF/27/P25/25.
It is normal that cycle times of the plow circuit EF/27/P25/25 slow down when
the spreader operates. Proper sizing of the pump 21 insures adequate flow to
all
functions under all circumstances.
The present invention provides a simple, flexible, reliable and affordable
system for the operation of a material spreader when it is used simultaneously
with
another hydraulically driven system like a snow plow.
3o While the invention has been described according to what is presently
considered to be the most practical and preferred embodiments, it must be
understood
that the invention is not limited to the disclosed embodiments. Those
ordinarily

CA 02390186 2002-07-02
skilled in the art will understand that various modifications and equivalent
structures
and functions may be made without departing from the spirit and scope of the
invention as defined in the claims. Therefore, the invention as defined in the
claims
must be accorded the broadest possible interpretation so as to encompass all
such
modifications and equivalent structures and functions.

Representative Drawing