[0001] The present invention relates to a differential-area pressure compensator and to
its control system of the hydraulic, mechanical or electro-hydraulic type.
[0002] Directional control valves, for controlling the fluid flow delivered to actuators
regardless of pressure, are widely used in hydraulics.
[0003] Such valves are commonly known as load sensing directional control valves or load
sensing control valves.
[0004] Flow sharing valves are a subset of these load sensing control valves.
[0005] They behave like any other load sensing control valve when the pump delivers enough
flow to meet the demand of the actuators; in addition, when the system is in a flow
saturation condition, they distribute the pump-delivered flow to all operating ports
proportionally to their demand, without causing any operating actuator to stop.
[0006] A detailed description of the operating principle of a particular load sensing, flow
sharing system is found in
US2006037649 or
US 3 937 129.
[0007] Load sensing control valves are of the closed center or open center type.
[0008] When no actuator is operated, i.e. in the standby state, open center load sensing
control valves discharge all the flow delivered by the pump, while closed center control
valves do not.
[0009] For this purpose, open center load sensing control valves have a pressure compensator
bypass-connected to the delivery line, which discharges the pump-delivered fluid flow
not demanded by the actuators; if the overall flow demanded by the actuators does
not exceed the flow delivered by the pump, then the pressure compensator discharges
the flow not demanded by the actuators at a delivery pressure that is equal to the
higher pressure among the served ports, usually named LS pressure, plus a pressure
margin depending on the compensator spring, e.g. 14 bar.
[0010] In the standby state, an open center load sensing control valve wastes a non negligible
amount of power, equal to the flow delivered by the pump multiplied by the pressure
margin .
[0011] DE 10 2004 014 113 A1 discloses a device for reducing the pressure margin in the standby state, thereby
providing energy savings.
[0012] Next to the pressure compensator 10, which imposes a pressure margin of 21 bar, there
is a pilot-operated compensator 12 which imposes a pressure margin of 3 bar and is
controlled by an LS pressure-controlled pilot valve 17.
[0013] When none of the actuators requires flow , i.e. the LS pressure is zero, the pressure
compensator 12 discharges all pump-delivered flow at the pressure of 3 bar, because
the pressure on the spring side 13 is the discharge pressure, the pilot valve 17 being
open; the pressure compensator 10 is closed because the delivery pressure does not
reach 21 bar.
[0014] When at least one actuator requires oil, i.e. when the LS pressure is greater than
zero, the pressure compensator 12 is in the closed position because the pressure on
the spring side 13 is the delivery pressure, the pilot valve 17 being closed; the
pressure compensator 10 discharges the flow not demanded by actuators at the pressure
of 21 bar plus the LS pressure.
[0015] This system involves an increased number of compensators as well as a more complex
construction, thereby leading to cost increase: the above mentioned patent application
requires two compensators, operating at different pressure values.
[0016] In this invention a valve, bypass-connected to the delivery line in a load sensing
control valve, discharges the pump-delivered fluid flow not demanded by the actuators
to the low pressure line, at a first (lower) value or a second (higher) value of pressure
margin, depending on how the valve is controlled by a hydraulic, mechanical or electrohydraulic
control system.
[0017] According to a first way of carrying out the pressure compensator with differential
areas controlled by a control system, the compensator is normally closed; it is biased
closed by a spring and by the LS pressure; it is biased open by two pressures respectively
exerted on two appropriately determined different areas, one subjected to the delivery
pressure and the other to the delivery pressure or the LS pressure depending on the
control system.
[0018] A first object of the present invention is to save energy in the standby state, by
decreasing the pressure margin from the operating state to the standby state and increasing
the pressure margin in the opposite case.
[0019] For this first object to be fulfilled, the control system is a three-way two-position
hydraulically actuated pilot valve, which is biased on one side by the LS pressure
and on the other side by a spring having a pressure rating of about 2 bar and by the
discharge pressure: when the LS pressure is zero, the pilot valve transmits the delivery
pressure to the compensator area controlled thereby; when the LS pressure is not zero,
it transmits the LS pressure.
[0020] A second object of the present invention is specific for load sensing, flow sharing
systems and consists in allowing the operator to select slow or fast operation of
the machine, for normal or fine motion of the actuators.
[0021] For this second object to be fulfilled, the control system is a three-way, two-position
mechanically or electrically actuated pilot valve which, like the hydraulic pilot
valve described above, transmits either the delivery pressure or the LS pressure to
the compensator area controlled thereby.
[0022] A third object of the present invention is specific for load sensing, flow sharing
systems and consists in simultaneously fulfilling the first and the second objects.
[0023] For this third object to be fulfilled, the control system is a three-way, two position
hydraulically actuated pilot valve, combined with a three-way two-position mechanically
or electrically actuated pilot valve: the hydraulically actuated pilot valve is biased
on one side by the LS pressure and on the other side by a spring having a pressure
rating of about 2 bar and by the discharge pressure so that, when the LS pressure
is zero, it transmits the delivery pressure, and when the LS pressure is not zero,
it transmits the LS pressure to the solenoid valve. The mechanically or electrically
actuated pilot valve in turn transmits the delivery pressure or the pressure it receives
from the hydraulically actuated three-way two-position pilot valve to the compensator
area controlled thereby.
[0024] According to a second way of carrying out the pressure compensator with differential
areas controlled by a control system, the compensator is normally closed; it is biased
open by the delivery pressure; it is biased closed by a spring and by two pressures
respectively exerted on two appropriately determined different areas, one subjected
to the LS pressure and the other to the delivery pressure or the LS pressure depending
on the control system.
[0025] Once again, in the second way of carrying out the pressure compensator with differential
areas, the control system can be designed to fulfill the first, second, or third objective.
[0026] These objects and advantages are achieved by the control systems for piloting the
pilot-operated differential-area pressure compensator according to this invention,
which is characterized by the annexed claims.
[0027] These and other features will be more apparent from the following description of
a few embodiments, which are shown by way of example and without limitation in the
accompanying drawings, in which:
- Figure 1 is a hydraulic diagram showing a first way of carrying out the differential-area
pressure compensator piloted by a control system, in which the control system is a
three-way two-position hydraulically actuated pilot valve;
- Figure 2 is a hydraulic diagram showing a variant of the control system of the pilot-operated
differential-area pressure compensator of Figure 1, in which the control system is
a three-way two-position electrically actuated pilot valve;
- Figure 3 is a hydraulic diagram showing a variant of the control system of the pilot-operated
differential-area pressure compensator as shown in Figures 1 and 2, in which the control
system is a three-way two-position hydraulically actuated valve in combination with
a three-way two-position electrically actuated pilot valve;
- Figure 4 is a hydraulic diagram showing a second way of carrying out the differential-area
pressure compensator piloted by a control system, in which the control system is a
three-way two-position hydraulically actuated pilot valve;
- Figure 5 shows a first embodiment according to the first way of carrying out the differential-area
pressure compensator shown in Figure 1;
- Figure 6 shows a second embodiment according to the second way of carrying out the
differential-area pressure compensator shown in Figure 4.
[0028] Figure 1 shows a hydraulic circuit, including a fixed-displacement pump 1, connected
by a high-pressure line P to a load sensing, flow sharing control valve V, which discharges
the fluid through a low pressure line T into the tank 2.
[0029] The load sensing, flow sharing control valve V has an inlet cover F and two elements
or sections E1 and E2, each controlling an actuator through the ports A1, B1 and A2,
B2.
[0030] A detailed description of the specific configuration of the load sensing, flow sharing
control valve V shown in figure may be found in patent application
US2006037649 A1 by the applicant hereof, therefore its architecture and working principle will be
only described shortly herein.
[0031] Each element has a spool 4, a local pressure compensator 3 comprising therein a signal
selector S, which is mechanically kept open or closed by a piston 5 with a spring
M of negligible force. The piston 5 presses against the compensator 3 of the element
E at the higher pressure in the control valve V, said compensator 3 and piston 5 thus
acting as a check valve, whereas, in the sections at lower pressure, the piston 5
is kept detached from the compensator 3, so that this latter performs its function
of pressure compensator.
[0032] As a rule, the amount of fluid flowing through an orifice is proportional to the
area of the orifice and to the square root of the pressure drop thereacross, assuming
the other factors are equal.
[0033] In load sensing, flow sharing control valves, flow rate is controlled by adjusting
the position of the spool, as the effective pressure drop across the flow rate control
or metering orifice of each spool is the same for all elements and is equal to pressure
margin, regardless of the pressure of loads. Pressure margin is a quasi constant value
under flow unsaturated conditions and decreases as saturation occurs.
[0034] Inside the inlet cover F, the high pressure line P is connected to the low pressure
line T through the differential-area pressure compensator C piloted through the control
line 15 by the control system S.
[0035] The compensator C is a two-way continuous position valve 6, which is biased closed
by a spring 7 and by the LS pressure exerted on the surface 8, and is biased open
by the pressure P exerted on the surface 9 and the control pressure of line 15 on
the surface 10.
[0036] Assuming that A8 designates the area of the control surface 8, A9 designates the
area of the control surface 9 and A10 designates the area of the control surface 10,
the valve 6 is designed in such a manner that the sum of the areas A9 and A10 is equal
to the area A8 of the control surface 8:
A9+
A10=
A8
[0037] The valve 6 can be designed in various manners within the functional arrangement
as set out above.
[0038] Figure 5 shows a first embodiment according to the first way of carrying out the
differential-area pressure compensator shown in fig. 1.
[0039] The control system S is a three-way, two-position pilot valve 11, whose spool is
piloted on the surface 13 by the pressure T and is biased by a spring 12 whose force
against the area of the control surface corresponds to about 2 bar; on the other surface
14 it is controlled by the LS pressure.
[0040] The pilot valve 11 normally transmits the pressure P to the surface 10 of the valve
6 through the control line 15, and it transmits the LS pressure when it is switched.
[0041] The differential-area compensator C, piloted by the control system S of Figure 1
sets the pressure margin to a first value from 3 to 7 bar, e.g. 5 bar, if the operator
does not actuate any spool, or to a second value from 14 to 25 bar, e.g. 14 bar, if
the operator actuates at least one spool, thereby allowing to save energy in the standby
state.
[0042] In the standby state, the LS pressure is zero, as no spool is operated. The pilot
valve 11 is in the position depicted in Figure 1 due to the bias of the spring 12,
and transmits the pressure P to the surface 10 of the valve 6 through the line 15.
[0043] Assuming that F7 designates the force of the spring 7, p
P is the delivery pressure and p
LS the LS pressure, then the balance of the valve 6 is given by the following relation:
[0044] Considering the relations between the areas:
[0045] Thence, the pressure margin p
P - p
LS is equal to a first value, corresponding to F7 / A8, in this example to 5 bar: therefore,
in the standby state, the differential-area compensator C controlled by the control
system S of Figure 1 discharges the whole flow delivered by the pump 1 at a pressure
of 5 bar.
[0046] When the operator actuates at least one spool, the LS pressure increases and switches
the pilot valve 11, whereby the control system S pilots the surface 10 of the valve
6 through the control line 15 with the LS pressure.
[0047] The balance of the valve 6 in this operating state is given by the following relation:
[0048] Whence:
[0049] Since A9 is smaller than A8, the second pressure margin value p
P - p
LS, in this example 14 bar, is higher than the former, therefore in operating conditions
the differential-area compensator C controlled by the control system S of Figure 1
discharges the pump-delivered flow not demanded by the active workports at a pressure
pp 14 bar higher than P
LS.
[0050] Figure 2 shows a load sensing, flow sharing control valve V comprising a pilot-operated
differential-area pressure compensator C as shown in Figure 1, in which the control
system S is a three-way two-position electrically actuated spool 17.
[0051] The spool 17 normally transmits the LS pressure through the control line 15 and,
in the excited position, it transmits the pressure P.
[0052] Thus, the control system S allows to set the pressure margin to two values, e.g.
5 and 14 bar.
[0053] In load sensing, flow sharing control valves, the flow to the port is proportional
to the square root of the pressure margin, assuming the other factors are equal, therefore
if the pressure margin decreases, flows to the workports are accordingly reduced,
for finer control of the machine.
[0054] In this case, unlike the configuration of Figure 1, pressure margin control depends
on the position of the electrically actuated spool 17, therefore on the operator,
who can select normal speed (normal control) or reduced speed (fine control) of the
machine actuators.
[0055] The operating principle is unchanged if the three-way two-position spool 17 is mechanically
or electrically controlled.
[0056] Figure 3 shows a load sensing, flow sharing control valve V comprising a pilot-operated
differential-area pressure compensator C as shown in Figures 1 and 2, and a control
system S in the form of a three-way two-position hydraulically actuated pilot valve
18 in combination with a three-way two-position electrically actuated spool 22.
[0057] The spool of the pilot valve 18 is piloted on the surface 20 by the pressure T and
is biased by a spring 19 whose force against the area of the control surface corresponds
to about 2 bar; on the other surface 21 it is controlled by the LS pressure. The pilot
valve 18 normally transmits the pressure P to the spool 22 through the line 23, and
it transmits the LS pressure when it is switched.
[0058] The spool 22 normally connects the line 23 to the control line 15 and, in the excited
position, it transmits the pressure P to the control line 15.
[0059] When the spool 22 is in the position shown in figure 3, the differential-area compensator
C, controlled by the control system S , sets the pressure margin to a first value,
e.g. 5 bar, if the operator does not actuate any spool, or to a second value, e.g.
14 bar, if the operator actuates at least one spool, thereby allowing to save energy
in the standby state; when the operator switches the spool 22, the pressure margin
is set to the first 5 bar value even in operating conditions, for fine control of
the machine actuators.
[0060] In Figure 4, the high pressure line P is connected to the low pressure line T through
the differential-area pressure compensator C piloted through the control line 33 by
the control system S.
[0061] The compensator C is a two-way continuous position valve 24, which is biased open
by the pressure P exerted on the surface 28, and is biased closed by a spring 25,
by the control pressure of 33 exerted on the surface 26 and by the LS pressure on
the surface 27.
[0062] Assuming that A26 designates the area of the control surface 26, A27 designates the
area of the control surface 27 and A28 designates the area of the control surface
28 the valve 24 is designed in such a manner that:
[0063] The valve 24 can be designed in various manners within the functional arrangement
as set out above.
[0064] Figure 6 shows an embodiment according to the second way of carrying out the differential-area
pressure compensator shown in fig. 4.
[0065] The control system S is a three-way, two-position pilot valve 29, whose spool is
piloted on the surface 31 by the discharge pressure p
T and is biased by a spring 30 whose force against the area of the control surface
corresponds to about 2 bar; on the other surface 32 it is piloted by the LS pressure.
The pilot valve 29 normally transmits the LS pressure to the surface 26 of the valve
24 through the control line 33, and it transmits the pressure pp when it is switched.
[0066] The differential-area compensator C, controlled by the control system S of Figure
4 sets the pressure margin to a first value from 3 to 7 bar, e.g. 5 bar, if the operator
does not actuate any spool, or to a second value from 14 to 25 bar, e.g. 14 bar, if
the operator actuates at least one spool, thereby allowing to save energy in the standby
state.
[0067] In the standby state, the LS pressure is zero, as no spool is operated. The pilot
valve 29 is in the position depicted in Figure 4 due to the bias of the spring 30,
and transmits the LS pressure to the surface 26 of the valve 24 through the line 33.
[0068] Assuming that F25 designates the force of the spring 25, then the balance of the
valve 24 is given by the following relation:
[0069] Whence:
[0070] The pressure margin pP - pLS is equal to a first value, corresponding to F25 / A28,
in this example to 5 bar, therefore, in the standby state, the differential-area compensator
C controlled by the control system S of Figure 4 discharges the whole flow delivered
by the pump 1 at a pressure of 5 bar.
[0071] When the operator actuates at least one spool, the LS pressure increases and switches
the valve 29, whereby the control system S pilots the surface 26 of the valve 24 through
the line 33 with the pressure pP.
[0072] The balance of the valve 6 in this operating state is given by the following relation:
[0073] Whence:
[0074] Since A27 is smaller than A28, the second pressure margin value pP - pLS is higher
than the former, in this example 14 bar, therefore in operating conditions the differential-area
compensator C piloted by the control system S of Figure 4 discharges the pump-delivered
flow not demanded by the workports at a pressure pP 14 bar higher than pLS.
[0075] The control systems described above for the compensator according to the first way
of carrying out the present invention can be easily used for the compensator of the
second way of carrying out the present invention.
[0076] Figure 5 shows an embodiment according to the first way of carrying out the differential-area
pressure compensator shown in Figure 1.
[0077] A passage 106 is formed in the body 108 of the inlet cover F, whose section has an
area A8 and within which the valve 6 slides between two plugs 115 and 116.
[0078] Two annular recesses 105 and 103 are provided within the passage 106: the recess
105 receives pressurized fluid through the high pressure P line from the pump 1; the
recess 103 is connected to the tank 2 through the low pressure T line.
[0079] The valve 6 normally closes the connection between the recesses, 105 and 103 because
its edge 111 covers the edge 110 of the body 108.
[0080] The spring 7 operates in the closing direction on the surface 8 of the valve 6 in
combination with the LS pressure reigning in the chamber 107, which is delimited by
the surface 8, the body 108 and the plug 116.
[0081] A bore 114, whose section has an area A9, is formed in the valve 6, on the opposite
side of the surface 8.
[0082] A piston 100, sliding within the bore 114, has two surfaces at its ends, the surface
112 on the side of the valve 6, and the surface 101 on the side of the plug 115.
[0083] The piston 100 delimits a chamber 113 between the surface 112 and the surface 9,
in which there is the pressure P, thanks to the holes 109 and 104 in the valve 6.
[0084] The surface 10 of the valve 6 and the surface 101 of the piston 100, with the body
108 and the plug 115, delimit the chamber 102, which receives the control pressure
of the valve 11 through the line 15.
[0085] When in the chamber 102 there is the LS pressure, the piston 100 is biased against
the plug 115 by the pressure pP in 113, and when in the chamber 102 there is the pressure
pP, the piston 100 is in neutral equilibrium. In both cases, the piston 100 exerts
no force on the valve 6, whose balanced state is determined by the pressures exerted
on the surfaces 8, 9 and 10 and by the spring 7, as explained in the description of
Figure 1.
[0086] Figure 6 shows an embodiment according to the second way of carrying out the differential-area
pressure compensator shown in Figure 4.
[0087] A bore 211 is formed in the body 209 of the inlet cover F, whose section has an area
A27 and within which the valve 204 slides.
[0088] Two recesses 205 and 203 are provided within the bore 211: the recess 205 receives
pressurized fluid through the high pressure P line from the pump 1; the recess 203
is connected to the tank 2 through the low pressure T line.
[0089] The valve 204 normally closes the connection between the recess 205 and the recess
203 because its edge 208 covers the edge 207 of the body 209.
[0090] The spring 25 operates in the closing direction on the surface 27 of the valve 204
in combination with the LS pressure reigning in the chamber 206, which is delimited
by the surface 27, the plug 215 and the body 209.
[0091] In the body 209, opposite to the surface 27, there is a passage 210, of greater diameter
than the bore 211, whose section has an area A28.
[0092] A piston 201 slides within the bore 210 and has two surfaces at its ends, the surface
212 on the side of the valve 204, and the surface 28 on the side of the plug 214.
[0093] The piston 201 delimits a chamber 200 with the surface 28, the body 209 and the plug
214, with the delivery pressure pP therein.
[0094] The surface 213 of the valve 204, the valve 204 itself and the surface 212 of the
piston 201, with the body 209, delimit the chamber 202, which receives the control
pressure of the valve 29 through the line 33.
[0095] When the pressure in the chamber 202 is the delivery pressure pP, the piston 201
is in neutral equilibrium. In this case, if A213 designates the area of the projection
of the surface 213 on a plane normal to the axis of the valve 204, the balance in
the axial direction of the valve 204 is given by the following relation:
[0096] Since A213 = A27, then:
[0097] When the pressure in the chamber 202 is the LS pressure, the piston 201 is pushed
against the valve 204 by the pressure pP in the chamber 200.
[0098] In this case, the valve 204 and the piston 201 are pressed one against the other
and, assuming that A212 designates the area of the surface 212, they are in equilibrium
in the following manner:
[0099] And since A213 = A27, A212 = A28:
[0100] In short, the operation of the preferred embodiment as shown in Figure 6 is similar
to that explained in the description of Figure 4, in fact the piston 201 and the valve
204, even though separated components to avoid the need for any coaxial grinding,
if thought as a single component lead to the valve 24 of Figure 4.
1. A differential-area pressure compensator (C) piloted by a control system (S), said
control system (S) being of the hydraulic, mechanical or electro-hydraulic type, in
a hydraulic load sensing control valve (V), comprising a high pressure (P) line, a
low pressure (T) line, and a line (LS) at the LS pressure of the higher load, said
two-way, continuous positioning, normally closed compensator (C) joining the high
pressure (P) line with the low pressure (T) line, said compensator (C) discharging
the pump-delivered fluid flow not demanded by the actuators to the low pressure (T)
line, the pressure margin at which it discharges the pump-delivered fluid flow not
demanded by the actuators being equal to a first value, from 3 to 7 bar, or a second
value, from 14 to 25 bar, depending on how said differential-area compensator (C)
is piloted by a control system (S), said compensator (C) being biased closed by the
action of a spring (7) and the LS pressure on a first surface (8) and being biased
open by the action of the delivery pressure (P) on a second surface (9) and by the
pilot pressure transmitted by the control system (S) on a third surface (10), the
sum of the areas of the latter two surfaces (9, 10) being equal to the area of the
former (8) and the pilot pressure of the control system (S) being equal to the delivery
pressure (P) or the LS pressure, characterized in that said control system (S) is a three-way two-position pilot valve (11) controlled by
the LS pressure which, when the LS pressure is zero, transmits the delivery pressure
to the surface (10) controlled thereby, whereas, when the LS pressure is not zero,
transmits the LS pressure.
2. A differential-area pressure compensator (C) piloted by a control system (S), said
control system (S) being of the hydraulic, mechanical or electro-hydraulic type, in
a hydraulic load sensing control valve (V), comprising a high pressure (P) line, a
low pressure (T) line, and a line (LS) at the LS pressure of the higher load, said
two-way, continuous positioning, normally closed compensator (C) joining the high
pressure (P) line with the low pressure (T) line, said compensator (C) discharging
the pump-delivered fluid flow not demanded by the actuators to the low pressure (T)
line, the pressure margin at which it discharges the pump-delivered fluid flow not
demanded by the actuators being equal to a first value, from 3 to 7 bar, or a second
value, from 14 to 25 bar, depending on how said differential-area compensator (C)
is piloted by a control system (S), said compensator (C) being biased closed by the
action of a spring (7) and the LS pressure on a first surface (8) and being biased
open by the action of the delivery pressure (P) on a second surface (9) and by the
pilot pressure transmitted by the control system (S) on a third surface (10), the
sum of the areas of the latter two surfaces (9, 10) being equal to the area of the
former (8) and the pilot pressure of the control system (S) being equal to the delivery
pressure (P) or the LS pressure, characterized in that said control system (S) is a three-way two-position electrically or mechanically
actuated pilot spool (17) which transmits the delivery pressure (P) or the LS pressure
to the surface (10) controlled thereby.
3. A differential-area pressure compensator (C) piloted by a control system (S), said
control system (S) being of the hydraulic, mechanical or electro-hydraulic type, in
a hydraulic load sensing control valve (V), comprising a high pressure (P) line, a
low pressure (T) line, and a line (LS) at the LS pressure of the higher load, said
two-way, continuous positioning, normally closed compensator (C) joining the high
pressure (P) line with the low pressure (T) line, said compensator (C) discharging
the pump-delivered fluid flow not demanded by the actuators to the low pressure (T)
line, the pressure margin at which it discharges the pump-delivered fluid flow not
demanded by the actuators being equal to a first value, from 3 to 7 bar, or a second
value, from 14 to 25 bar, depending on how said differential-area compensator (C)
is piloted by a control system (S), said compensator (C) being biased closed by the
action of a spring (7) and the LS pressure on a first surface (8) and being biased
open by the action of the delivery pressure (P) on a second surface (9) and by the
pilot pressure transmitted by the control system (S) on a third surface (10), the
sum of the areas of the latter two surfaces (9, 10) being equal to the area of the
former (8) and the pilot pressure of the control system (S) being equal to the delivery
pressure (P) or the LS pressure, characterized in that said control system (S) is a three-way two-position valve (18) controlled by the
LS pressure in combination with a three-way two-position electrically or mechanically
actuated spool (22), the hydraulic pilot valve (18) transmitting to the spool (22)
the delivery pressure (P) when the LS pressure is zero, or the LS pressure when the
LS pressure is not zero, and the spool (22) transmitting in turn the delivery pressure
(P) or the pressure it receives from the three-way two-position valve (18) controlled
by the LS pressure to the surface (10).
4. A differential-area pressure compensator (C) piloted by a control system (S), said
control system (S) being of the hydraulic, mechanical or electro-hydraulic type, in
a hydraulic load sensing control valve (V), comprising a high pressure (P) line, a
low pressure (T) line, and a line (LS) at the LS pressure of the higher load, said
two-way, continuous positioning, normally closed compensator (C) joining the high
pressure (P) line with the low pressure (T) line, said compensator (C) discharging
the pump-delivered fluid flow not demanded by the actuators to the low pressure (T)
line, the pressure margin at which it discharges the pump-delivered fluid flow not
demanded by the actuators being equal to a first value, from 3 to 7 bar, or a second
value, from 14 to 25 bar, depending on how said differential-area compensator (C)
is piloted by a control system (S), said compensator (C) being biased open by the
action of the delivery pressure (P) on a first surface (28) and being biased closed
by the action of a spring (25), of the LS pressure on a second surface (27) and of
the control transmitted by a control system (S) on a third surface (26), the sum of
the areas of the latter two surfaces (27, 26) being equal to the area of the former
(28) and the pilot pressure of the control system (S) being equal to the delivery
pressure (P) or the LS pressure, characterized in that said control system (S) is a three-way two-position pilot valve (29) piloted by the
LS pressure which, when the LS pressure is zero, transmits the LS pressure to the
surface (26) controlled thereby, whereas, when the LS pressure is not zero, transmits
the delivery pressure.
5. A differential-area pressure compensator (C) piloted by a control system (S), said
control system (S) being of the hydraulic, mechanical or electro-hydraulic type, in
a hydraulic load sensing control valve (V), comprising a high pressure (P) line, a
low pressure (T) line, and a line (LS) at the LS pressure of the higher load, said
two-way, continuous positioning, normally closed compensator (C) joining the high
pressure (P) line with the low pressure (T) line, said compensator (C) discharging
the pump-delivered fluid flow not demanded by the actuators to the low pressure (T)
line, the pressure margin at which it discharges the pump-delivered fluid flow not
demanded by the actuators being equal to a first value, from 3 to 7 bar, or a second
value, from 14 to 25 bar, depending on how said differential-area compensator (C)
is piloted by a control system (S), said compensator (C) being biased open by the
action of the delivery pressure (P) on a first surface (28) and being biased closed
by the action of a spring (25), of the LS pressure on a second surface (27) and of
the control transmitted by a control system (S) on a third surface (26), the sum of
the areas of the latter two surfaces (27, 26) being equal to the area of the former
(28) and the pilot pressure of the control system (S) being equal to the delivery
pressure (P) or the LS pressure, characterized in that said control system (S) is a three-way two-position electrically or mechanically
actuated pilot valve, which transmits the delivery pressure (P) or the LS pressure
to the surface (26) controlled thereby.
6. A differential-area pressure compensator (C) piloted by a control system (S), said
control system (S) being of the hydraulic, mechanical or electro-hydraulic type, in
a hydraulic load sensing control valve (V), comprising a high pressure (P) line, a
low pressure (T) line, and a line (LS) at the LS pressure of the higher load, said
two-way, continuous positioning, normally closed compensator (C) joining the high
pressure (P) line with the low pressure (T) line, said compensator (C) discharging
the pump-delivered fluid flow not demanded by the actuators to the low pressure (T)
line, the pressure margin at which it discharges the pump-delivered fluid flow not
demanded by the actuators being equal to a first value, from 3 to 7 bar, or a second
value, from 14 to 25 bar, depending on how said differential-area compensator (C)
is piloted by a control system (S), said compensator (C) being biased open by the
action of the delivery pressure (P) on a first surface (28) and being biased closed
by the action of a spring (25), of the LS pressure on a second surface (27) and of
the control transmitted by a control system (S) on a third surface (26), the sum of
the areas of the latter two surfaces (27, 26) being equal to the area of the former
(28) and the pilot pressure of the control system (S) being equal to the delivery
pressure (P) or the LS pressure, characterized in that said control system (S) is a three-way two-position hydraulic pilot valve controlled
by the LS pressure, in combination with a three-way two-position manually or electrically
actuated valve, the hydraulic pilot valve transmitting to the solenoid valve the LS
pressure when the LS pressure is zero, or the delivery pressure (P) when the LS pressure
is not zero, and the solenoid valve transmitting in turn the LS pressure or the pressure
it receives from the three-way two-position valve controlled by the LS pressure to
the surface (26).
7. A compensator (C) as claimed in claim 4 or 5 or 6,
characterized in that, it is composed of a valve (204) and a piston (201) of greater diameter than the
spool of the valve (204):
- said valve (204) being biased closed by the spring (25) and by the LS pressure,
and biased open by the pilot pressure of the control system (S) and by the piston
(201),
- said piston (201) being pushed on one side by the valve (204) and by the pilot pressure
of the control system (S) and on the other side by the pressure of the high pressure
(P) line.
1. Von einem Kontrollsystem (S) gesteuerter Differenz-Flächen-Druckausgleicher (C), wobei
das gesagte Kontrollsystem (S) des hydraulischen, mechanischen oder elektro-hydraulischen
Typs ist, in einem gegen eine hydraulische Ladung empfindlichen Kontrollventil (V),
enthaltend eine Hochdruckleitung (P), eine Niederdruckleitung (T), und eine Leitung
(LS) bei dem LS Druck der höheren Ladung, wobei der gesagte üblicherweise geschlossene
und dauerhaft ausrichtende Zwei-Weg-Ausgleicher (C) die Hochdruckleitung (P) mit der
Niederdruckleitung (T) verbindet, wobei der gesagte Ausgleicher (C) den von einer
Pumpe gelieferten und nicht von den Aktoren geforderten Fluss einer Flüssigkeit zur
Niederdruckleitung (T) auslädt, und wobei die Druckgrenze bei der er den von der Pumpe
gelieferten und nicht von den Aktoren geforderten Fluss der Flüssigkeit gleich einem
ersten Wert von 3 bis 7 bar ist, oder einem zweiten Wert von 14 bis 25 bar ist, in
Abhängigkeit davon, wie der gesagte Differenz-Flächen-Ausgleicher (C) von einem Kontrollsystem
(S) gesteuert wird, wobei der gesagte Ausgleicher (C) von der Wirkung einer Feder
(7) und des LS Druckes auf einer ersten Oberfläche (8) in Richtung eines Schließens
beaufschlagt ist und von der Wirkung des Lieferdruckes (P) auf einer zweiten Oberfläche
(9) und von dem vom Kontrollsystem (S) auf einer dritten Oberfläche (10) übertragenen
Pilotdruck beaufschlagt ist, wobei die Summe der Flächen der letzten zwei Oberflächen
(9, 10) gleich der Fläche der ersten ist, und wobei der Pilotdruck des Kontrollsystems
(S) gleich dem Lieferdruck (P) oder dem LS Druck ist, dadurch gekennzeichnet, dass das gesagte Kontrollsystem ein 3-Weg- 2-Stellung- Pilotventil (11) ist, gesteuert
vom Niederdruck LS, das wenn der LS Druck gleich Null ist, den Lieferdruck der von
ihm kontrollierter Oberfläche (10) überträgt, während, wenn der LS Druck ungleich
Null ist, den LS Druck überträgt.
2. Von einem Kontrollsystem (S) gesteuerter Differenz-Flächen-Druckausgleicher (C), wobei
das gesagte Kontrollsystem (S) des hydraulischen, mechanischen oder elektro-hydraulischen
Typs ist, in einem gegen eine hydraulische Ladung empfindlichen Kontrollventil (V),
enthaltend eine Hochdruckleitung (P), eine Niederdruckleitung (T), und eine Leitung
(LS) bei dem LS Druck der höheren Ladung, wobei der gesagte üblicherweise geschlossene
und dauerhaft ausrichtende Zwei-Weg-Ausgleicher (C) die Hochdruckleitung (P) mit der
Niederdruckleitung (T) verbindet, wobei der gesagte Ausgleicher (C) den von einer
Pumpe gelieferten und nicht von den Aktoren geforderten Fluss einer Flüssigkeit zur
Niederdruckleitung (T) auslädt, und wobei die Druckgrenze bei der er den von der Pumpe
gelieferten und nicht von den Aktoren geforderten Fluss der Flüssigkeit gleich einem
ersten Wert von 3 bis 7 bar ist, oder einem zweiten Wert von 14 bis 25 bar ist, in
Abhängigkeit davon, wie der gesagte Differenz-Flächen-Ausgleicher (C) von einem Kontrollsystem
(S) gesteuert wird, wobei der gesagte Ausgleicher (C) von der Wirkung einer Feder
(7) und des LS Druckes auf einer ersten Oberfläche (8) in Richtung eines Schließens
beaufschlagt ist und von der Wirkung des Lieferdruckes (P) auf einer zweiten Oberfläche
(9) und von dem vom Kontrollsystem (S) auf einer dritten Oberfläche (10) übertragenen
Pilotdruck beaufschlagt ist, wobei die Summe der Flächen der letzten zwei Oberflächen
(9, 10) gleich der Fläche der ersten ist, und wobei der Pilotdruck des Kontrollsystems
(S) gleich dem Lieferdruck (P) oder dem LS Druck ist, dadurch gekennzeichnet, dass das gesagte Kontrollsystem ein 3-Weg- 2-Stellung- Pilotspule (17) ist, elektrisch
oder mechanisch gesteuert, die den Lieferdruck (P) oder den LS Druck der von ihm gesteuerten
Oberfläche überträgt.
3. Von einem Kontrollsystem (S) gesteuerter Differenz-Flächen-Druckausgleicher (C), wobei
das gesagte Kontrollsystem (S) des hydraulischen, mechanischen oder elektro-hydraulischen
Typs ist, in einem gegen eine hydraulische Ladung empfindlichen Kontrollventil (V),
enthaltend eine Hochdruckleitung (P), eine Niederdruckleitung (T), und eine Leitung
(LS) bei dem LS Druck der höheren Ladung, wobei der gesagte üblicherweise geschlossene
und dauerhaft ausrichtende Zwei-Weg-Ausgleicher (C) die Hochdruckleitung (P) mit der
Niederdruckleitung (T) verbindet, wobei der gesagte Ausgleicher (C) den von einer
Pumpe gelieferten und nicht von den Aktoren geforderten Fluss einer Flüssigkeit zur
Niederdruckleitung (T) auslädt, und wobei die Druckgrenze bei der er den von der Pumpe
gelieferten und nicht von den Aktoren geforderten Fluss der Flüssigkeit gleich einem
ersten Wert von 3 bis 7 bar ist, oder einem zweiten Wert von 14 bis 25 bar ist, in
Abhängigkeit davon, wie der gesagte Differenz-Flächen-Ausgleicher (C) von einem Kontrollsystem
(S) gesteuert wird, wobei der gesagte Ausgleicher (C) von der Wirkung einer Feder
(7) und des LS Druckes auf einer ersten Oberfläche (8) in Richtung eines Schließens
beaufschlagt ist und von der Wirkung des Lieferdruckes (P) auf einer zweiten Oberfläche
(9) und von dem vom Kontrollsystem (S) auf einer dritten Oberfläche (10) übertragenen
Pilotdruck beaufschlagt ist, wobei die Summe der Flächen der letzten zwei Oberflächen
(9, 10) gleich der Fläche der ersten ist, und wobei der Pilotdruck des Kontrollsystems
(S) gleich dem Lieferdruck (P) oder dem LS Druck ist, dadurch gekennzeichnet, dass das gesagte Kontrollsystem ein 3-Weg- 2-Stellung- Pilotventil (18) ist, gesteuert
vom LS Druck, in Verbindung mit einer 3-Weg- 2-Stellung-Pilotspule (22), elektrisch
oder mechanisch gesteuert, wobei das hydraulische Pilotventil (18) der Spule (22)
den Lieferdruck (22) überträgt, wenn der LS Druck gleich Null ist, oder den LS Druck
wenn der LS Druck ungleich Null ist, und wobei die Spule (22) jeweils den Lieferdruck
(P) oder den Druck überträgt, den es vom 3-Weg 2-Stellung- Ventil (18) empfängt und
gesteuert vom LS Druck auf der Oberfläche (10) ist.
4. Von einem Kontrollsystem (S) gesteuerter Differenz-Flächen-Druckausgleicher (C), wobei
das gesagte Kontrollsystem (S) des hydraulischen, mechanischen oder elektro-hydraulischen
Typs ist, in einem gegen eine hydraulische Ladung empfindlichen Kontrollventil (V),
enthaltend eine Hochdruckleitung (P), eine Niederdruckleitung (T), und eine Leitung
(LS) bei dem LS Druck der höheren Ladung, wobei der gesagte üblicherweise geschlossene
und dauerhaft ausrichtende Zwei-Weg-Ausgleicher (C) die Hochdruckleitung (P) mit der
Niederdruckleitung (T) verbindet, wobei der gesagte Ausgleicher (C) den von einer
Pumpe gelieferten und nicht von den Aktoren geforderten Fluss einer Flüssigkeit zur
Niederdruckleitung (T) auslädt, und wobei die Druckgrenze bei der er den von der Pumpe
gelieferten und nicht von den Aktoren geforderten Fluss der Flüssigkeit gleich einem
ersten Wert von 3 bis 7 bar ist, oder einem zweiten Wert von 14 bis 25 bar ist, in
Abhängigkeit davon, wie der gesagte Differenz-Flächen-Ausgleicher (C) von einem Kontrollsystem
(S) gesteuert wird, wobei der gesagte Ausgleicher (C) von der Wirkung des Lieferdruckes
(P) auf einer ersten Oberfläche (28) in Richtung eines Öffnens beaufschlagt ist und
von der Wirkung einer Feder (25), des LS Druckes auf einer zweiten Oberfläche (27)
und von dem vom Kontrollsystem (S) auf einer dritten Oberfläche (26) übertragenen
Steuerung in Richtung eines Schließens beaufschlagt ist, wobei die Summe der Flächen
der letzten zwei Oberflächen (27, 26) gleich der Fläche der ersten (28) ist, und wobei
der Pilotdruck des Kontrollsystems (S) gleich dem Lieferdruck (P) oder dem LS Druck
ist, dadurch gekennzeichnet, dass das gesagte Kontrollsystem ein 3-Weg- 2-Stellung- Pilotventil (29) ist, gesteuert
vom LS Druck, in Verbindung mit einer 3-Weg- 2-Stellung-Pilotspule (22), das, wenn
der LS Druck gleich Null ist, den LS Druck auf der von ihm gesteuerten Oberfläche
überträgt, während wenn der LS Druck ungleich Null ist, den Lieferdruck überträgt.
5. Von einem Kontrollsystem (S) gesteuerter Differenz-Flächen-Druckausgleicher (C), wobei
das gesagte Kontrollsystem (S) des hydraulischen, mechanischen oder elektro-hydraulischen
Typs ist, in einem gegen eine hydraulische Ladung empfindlichen Kontrollventil (V),
enthaltend eine Hochdruckleitung (P), eine Niederdruckleitung (T), und eine Leitung
(LS) bei dem LS Druck der höheren Ladung, wobei der gesagte üblicherweise geschlossene
und dauerhaft ausrichtende Zwei-Weg-Ausgleicher (C) die Hochdruckleitung (P) mit der
Niederdruckleitung (T) verbindet, wobei der gesagte Ausgleicher (C) den von einer
Pumpe gelieferten und nicht von den Aktoren geforderten Fluss einer Flüssigkeit zur
Niederdruckleitung (T) auslädt, und wobei die Druckgrenze bei der er den von der Pumpe
gelieferten und nicht von den Aktoren geforderten Fluss der Flüssigkeit gleich einem
ersten Wert von 3 bis 7 bar ist, oder einem zweiten Wert von 14 bis 25 bar ist, in
Abhängigkeit davon, wie der gesagte Differenz-Flächen-Ausgleicher (C) von einem Kontrollsystem
(S) gesteuert wird, wobei der gesagte Ausgleicher (C) von der Wirkung des Lieferdruckes
(P) auf einer ersten Oberfläche (28) in Richtung eines Öffnens beaufschlagt ist und
von der Wirkung einer Feder (25), des LS Druckes auf einer zweiten Oberfläche (27)
und von dem vom Kontrollsystem (S) auf einer dritten Oberfläche (26) Steuerung in
Richtung eines Schließens beaufschlagt ist, wobei die Summe der Flächen der letzten
zwei Oberflächen (27, 26) gleich der Fläche der ersten (28) ist, und wobei der Pilotdruck
des Kontrollsystems (S) gleich dem Lieferdruck (P) oder dem LS Druck ist, dadurch gekennzeichnet, dass das gesagte Kontrollsystem ein 3-Weg- 2-Stellung-Pilotventil, elektrisch oder mechanisch
gesteuert, das den Lieferdruck (P) oder den LS Druck auf der von ihm gesteuerten Oberfläche
(26) überträgt.
6. Von einem Kontrollsystem (S) gesteuerter Differenz-Flächen-Druckausgleicher (C), wobei
das gesagte Kontrollsystem (S) des hydraulischen, mechanischen oder elektro-hydraulischen
Typs ist, in einem gegen eine hydraulische Ladung empfindlichen Kontrollventil (V),
enthaltend eine Hochdruckleitung (P), eine Niederdruckleitung (T), und eine Leitung
(LS) bei dem LS Druck der höheren Ladung, wobei der gesagte üblicherweise geschlossene
und dauerhaft ausrichtende Zwei-Weg-Ausgleicher (C) die Hochdruckleitung (P) mit der
Niederdruckleitung (T) verbindet, wobei der gesagte Ausgleicher (C) den von einer
Pumpe gelieferten und nicht von den Aktoren geforderten Fluss einer Flüssigkeit zur
Niederdruckleitung (T) auslädt, und wobei die Druckgrenze bei der er den von der Pumpe
gelieferten und nicht von den Aktoren geforderten Fluss der Flüssigkeit gleich einem
ersten Wert von 3 bis 7 bar ist, oder einem zweiten Wert von 14 bis 25 bar ist, in
Abhängigkeit davon, wie der gesagte Differenz-Flächen-Ausgleicher (C) von einem Kontrollsystem
(S) gesteuert wird, wobei der gesagte Ausgleicher (C) von der Wirkung des Lieferdruckes
(P) auf einer ersten Oberfläche (28) in Richtung eines Öffnens beaufschlagt ist und
von der Wirkung einer Feder (25), des LS Druckes auf einer zweiten Oberfläche (27)
und von dem vom Kontrollsystem (S) auf einer dritten Oberfläche (26) Steuerung in
Richtung eines Schließens beaufschlagt ist, wobei die Summe der Flächen der letzten
zwei Oberflächen (27, 26) gleich der Fläche der ersten (28) ist, und wobei der Pilotdruck
des Kontrollsystems (S) gleich dem Lieferdruck (P) oder dem LS Druck ist, dadurch gekennzeichnet, dass das gesagte Kontrollsystem ein 3-Weg- 2-Stellunghydraulisches Pilotventil, vom LS
Druck gesteuert, in Verbindung mit einem 3-Weg- 2-Stellung- manuell oder elektrisch
gesteuerten Ventil, wobei das hydraulische Pilotventil dem Solenoid-Ventil den LS
Druck überträgt wenn der LS Druck gleich Null ist, oder den Lieferdruck (P) wenn der
LS Druck ungleich Null ist, und das Solenoid-Ventil jeweils den LS Druck oder den
Druck überträgt, den es vom 3-Weg- 2-Stellung- Ventil empfängt, vom LS Druck gesteuert
auf der Oberfläche (26).
7. Ausgleicher (C) nach Anspruch 4 oder 5 oder 6,
dadurch gekennzeichnet, dass es aus einem Ventil (204) und einem Kolben (201) besteht, deren Durchmesser grösser
als die Spule des Ventils (204) ist;
- das gesagte Ventil (204) wird von der Feder (25) und von dem LS Druck beaufschlagt,
und ist mittels des Pilotdruckes des Kontrollsystems (S) und des Kolbens (201) offen
gehalten,
- der gesagte Kolben (201) wird auf einer Seite von dem Ventil (204) und von dem Pilotdruck
des Kontrollsystems gedrückt, und auf der anderen Seite von dem Druck der Hochdruckleitung
(P) gedrückt.
1. Un compensateur (C) de pression à surface différentielle piloté par un système de
contrôle (S), le dit système de contrôle (S) étant du type hydraulique, mécanique
ou électro-hydraulique, dans une soupape (V) hydraulique sensible à une charge hydraulique,
comprenant un conduit (P) à haute pression, un conduit (T) à basse pression et un
conduit (LS) à la pression (LS) de la charge supérieure, le dit compensateur (C) à
deux voies, à positionnement continu et normalement fermé réunissant le conduit (P)
à haute pression avec le conduit (T) à basse pression, le dit compensateur (C) déchargeant
le flux d'un fluide actionné par une pompe et non demandé par les actuateurs au conduit
(T) à basse pression, la marge de pression à la quelle il décharge le flux du fluide
actionné par la pompe et non demandé par les actuateurs étant égale à une première
valeur, entre 3 et 7 bar, ou à une deuxième valeur, entre 14 et 25 bar, en fonction
de la manière avec la quelle le dit compensateur (C) à surface différentielle est
piloté par un système de contrôle (S), le dit compensateur (C) étant activé en fermeture
par action d'un ressort (7) et de la pression LS sur une première surface (8) et étant
activé en ouverture par action de la pression de livraison (P) sur une deuxième surface
(9) et par la pression pilote transmise par le système de contrôle (S) sur une troisième
surface (10), la somme des aires des deux dernières surfaces (9, 10) étant égale à
l'aire de la première (8) et la pression pilote du système de contrôle (S) étant égale
à la pression de livraison (P) ou à la pression LS, caractérisé en ce que le dit système de contrôle (S) est une soupape pilote (11) à trois voies et à deux
positions commandée par la pression LS qui, quand la pression LS est zéro, transmet
la pression de livraison à la surface (10) commandée par celle-ci, pendant que, quand
la pression LS n'est pas zéro, il transmet la pression LS.
2. Un compensateur (C) de pression à surface différentielle piloté par un système de
contrôle (S), le dit système de contrôle (S) étant du type hydraulique, mécanique
ou électro-hydraulique, dans une soupape (V) hydraulique sensible à une charge hydraulique,
comprenant un conduit (P) à haute pression, un conduit (T) à basse pression et un
conduit (LS) à la pression (LS) de la charge supérieure, le dit compensateur (C) à
deux voies, à positionnement continu et normalement fermé réunissant le conduit (P)
à haute pression avec le conduit (T) à basse pression, le dit compensateur (C) déchargeant
le flux d'un fluide activé par une pompe et non demandé par les actuateurs au conduit
(T) à basse pression, la marge de pression à la quelle il décharge le flux du fluide
activé par la pompe et non demandé par les actuateurs étant égale à une première valeur,
entre 3 et 7 bar, ou à une deuxième valeur, entre 14 et 25 bar, en fonction de la
manière avec laquelle le dit compensateur (C) à surface différentielle est piloté
par un système de contrôle (S), le dit compensateur (C) étant activé en fermeture
par action d'un ressort (7) et de la pression LS sur une première surface (8) et étant
activé en ouverture par action de la pression de livraison (P) sur une deuxième surface
(9) et par la pression pilote transmise par le système de contrôle (S) sur une troisième
surface (10), la somme des aires des deux dernières surfaces (9, 10) étant égale à
l'aire de la première (8) et la pression pilote du système de contrôle (S) étant égale
à la pression de livraison (P) ou à la pression LS, caractérisé en ce que le dit système de contrôle (S) est une bobine pilote (17) à trois voies et à deux
positions commandée électriquement ou mécaniquement qui transmet la pression de livraison
(P) ou la pression LS à la surface (10) commandée par celle-ci.
3. Un compensateur (C) de pression à surface différentielle piloté par un système de
contrôle (S), le dit système de contrôle (S) étant du type hydraulique, mécanique
ou électro-hydraulique, dans une soupape (V) hydraulique sensible à une charge hydraulique,
comprenant un conduit (P) à haute pression, un conduit (T) à basse pression et un
conduit (LS) à la pression LS de la charge supérieure, le dit compensateur (C) à deux
voies, à positionnement continu et normalement fermé réunissant le conduit (P) à haute
pression avec le conduit (T) à basse pression, le dit compensateur (C) déchargeant
le flux d'un fluide activé par une pompe et non demandé par les actuateurs au conduit
(T) à basse pression, la marge de pression à la quelle il décharge le flux du fluide
activé par la pompe et non demandé par les actuateurs étant égale à une première valeur,
entre 3 et 7 bar, ou à une deuxième valeur, entre 14 et 25 bar, en fonction de la
manière avec laquelle le dit compensateur (C) à surface différentielle est piloté
par un système de contrôle (S), le dit compensateur (C) étant activé en fermeture
par action d'un ressort (7) et de la pression LS sur une première surface (8) et étant
activé en ouverture par action de la pression de livraison (P) sur une deuxième surface
(9) et par la pression pilote transmise par le système de contrôle (S) sur une troisième
surface (10), la somme des aires des deux dernières surfaces (9, 10) étant égale à
l'aire de la première (8) et la pression pilote du système de contrôle (S) étant égale
à la pression de livraison (P) ou à la pression LS, caractérisé en ce que le dit système de contrôle (S) est une soupape (18) à trois voies et à deux positions
commandée par la pression LS en combinaison avec une bobine (22) à trois voies et
à deux positions commandée électriquement ou mécaniquement, la soupape pilote hydraulique
(18) transmettant à la bobine (22) la pression de livraison (P) quand la pression
LS est zéro, ou la pression LS quand la pression LS n'est pas zéro, et la bobine (22)
transmettant à sa fois la pression de livraison (P ) ou la pression qui elle reçoit
par la soupape (18) à trois voies et à deux positions commandée par la pression LS
à la surface (10).
4. Un compensateur (C) de pression à surface différentielle piloté par un système de
contrôle (S), le dit système de contrôle (S) étant du type hydraulique, mécanique
ou électro-hydraulique, dans une soupape (V) hydraulique sensible à une charge hydraulique,
comprenant un conduit (P) à haute pression, un conduit (T) à basse pression et un
conduit (LS) à la pression LS de la charge supérieure, le dit compensateur (C) à deux
voies, à positionnement continu et normalement fermé réunissant le conduit (P) à haute
pression avec le conduit (T) à basse pression, le dit compensateur (C) déchargeant
le flux d'un fluide activé par une pompe et non demandé par les actuateurs au conduit
(T) à basse pression, la marge de pression à laquelle il décharge le flux du fluide
activé par la pompe et non demandé par les actuateurs étant égale à une première valeur,
entre 3 et 7 bar, ou à une deuxième valeur, entre 14 et 25 bar, en fonction de la
manière avec laquelle le dit compensateur (C) à surface différentielle est piloté
par un système de contrôle (S), le dit compensateur (C) étant activé en ouverture
par action de la pression de livraison (P) sur une première surface (28) et étant
activé en fermeture par action d'un ressort (25), de la pression LS sur une deuxième
surface (27) et de la commande transmise par un système de contrôle (S) sur une troisième
surface (26), la somme des aires des deux dernières surfaces (27, 26) étant égale
à l'aire de la première (28) et la pression pilote du système de contrôle (S) étant
égale à la pression de livraison (P) ou à la pression LS, caractérisé en ce que le dit système de contrôle (S) est une soupape (29) à trois voies et à deux positions
pilotée par la pression LS qui, quand la pression LS est zéro, transmet la pression
LS à la surface (26) contrôlée par celle-ci, pendant que, quand la pression LS n'est
pas zéro, transmet la pression de livraison.
5. Un compensateur (C) de pression à surface différentielle piloté par un système de
contrôle (S), le dit système de contrôle (S) étant du type hydraulique, mécanique
ou électro-hydraulique, dans une soupape (V) hydraulique sensible à une charge hydraulique,
comprenant un conduit (P) à haute pression, un conduit (T) à basse pression et un
conduit (LS) à la pression LS de la charge supérieure, le dit compensateur (C) à deux
voies, à positionnement continu et normalement fermé réunissant le conduit (P) à haute
pression avec le conduit (T) à basse pression, le dit compensateur (C) déchargeant
le flux d'un fluide activé par une pompe et non demandé par les actuateurs au conduit
(T) à basse pression, la marge de pression à la quelle il décharge le flux du fluide
activé par la pompe et non demandé par les actuateurs étant égale à une première valeur,
entre 3 et 7 bar, ou à une deuxième valeur, entre 14 et 25 bar, en fonction de la
manière avec laquelle le dit compensateur (C) à surface différentielle est piloté
par un système de contrôle (S), le dit compensateur (C) étant activé en ouverture
par action de la pression de livraison (P) sur une première surface (28) et étant
activé en fermeture par action d'un ressort (25), de la pression LS sur une deuxième
surface (27) et de la commande transmise par un système de contrôle (S) sur une troisième
surface (26), la somme des aires des deux dernières surfaces (27, 26) étant égale
à l'aire de la première (28) et la pression pilote du système de contrôle (S) étant
égale à la pression de livraison (P) ou à la pression LS, caractérisé en ce que le dit système de contrôle (S) est une soupape pilote à trois voies et à deux positions
commandée électriquement ou mécaniquement, qui transmet la pression de livraison (P)
ou la pression LS à la surface (26) commandée par celle-ci.
6. Un compensateur (C) de pression à surface différentielle piloté par un système de
contrôle (S), le dit système de contrôle (S) étant du type hydraulique, mécanique
ou électro-hydraulique, dans une soupape (V) hydraulique sensible à une charge hydraulique,
comprenant un conduit (P) à haute pression, un conduit (T) à basse pression et un
conduit (LS) à la pression LS de la charge supérieure, le dit compensateur (C) à deux
voies, à positionnement continu et normalement fermé réunissant le conduit (P) à haute
pression avec le conduit (T) à basse pression, le dit compensateur (C) déchargeant
le flux d'un fluide activé par une pompe et non demandé par les actuateurs au conduit
(T) à basse pression, la marge de pression à la quelle il décharge le flux du fluide
activé par la pompe et non demandé par les actuateurs étant égale à une première valeur,
entre 3 et 7 bar, ou à une deuxième valeur, entre 14 et 25 bar, en fonction de la
manière avec laquelle le dit compensateur (C) à surface différentielle est piloté
par un système de contrôle (S), le dit compensateur (C) étant activé en ouverture
par action de la pression de livraison (P) sur une première surface (28) et étant
activé en fermeture par action d'un ressort (25), de la pression LS sur une deuxième
surface (27) et de la commande transmise par un système de contrôle (S) sur une troisième
surface (26), la somme des aires des deux dernières surfaces (27, 26) étant égale
à l'aire de la première (28) et la pression pilote du système de contrôle (S) étant
égale à la pression de livraison (P) ou à la pression LS, caractérisé en ce que le dit système de contrôle (S) est une soupape pilote hydraulique à trois voies et
à deux positions commandée par la pression LS, in combinaison avec une soupape à trois
voies et à deux positions activé manuellement ou électriquement, la soupape pilote
hydraulique transmettant à la soupape à solénoïde la pression LS quand la pression
LS est zéro, ou la pression de livraison (P) quand la pression LS n'est pas zéro,
et la soupape à solénoïde transmettant à sa fois la pression LS ou la pression qu'elle
reçoit de la soupape à trois voies et à deux positions commandée par la pression LS
à la surface (26).
7. Un compensateur (C) selon les revendications 4 ou 5 ou 6,
caractérisé en ce qu'il est composé par une soupape (204) et un piston (201) avec un diamètre supérieur
à la bobine de la soupape (204) ;
- la dite soupape (204) étant activée en fermeture par le ressort (25) et par a pression
LS, et étant activée en ouverture par la pression pilote du système de contrôle (S)
et du piston (201),
- le dit piston (201) étant poussé sur un côté par la soupape (204) et par la pression
pilote du système de contrôle (S) et sur l'autre côté par la pression du conduit (P
) à haute pression.