Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1086356
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THIS INVENTION relates to a method of bleeding an
hydraulic system and to apparatus for use therewith. It relates
in particular to a method of and apparatus for bleeding an
hydraulic system which comprises a master cylinder and piston
. assembly, a slave cylinder and piston assembly, and an hydraulic
i~ . line connecting the master cylinder to the slave cylinder for
.~ operatively conducting fluid between them. The method and
apparatus therefore finds particular use in bleeding the
~, hydraulic brake systems of motor vehicles.
By the tèrm "bleeding" lS to be understood the
. removal of air, dirt, or other contaminants from the hydraulic
system, or charging, purging, or flushing the system with --
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1~:J86356
clear, uncontaminated hydraulic fluid, i.e. hydraulic fluid
which is free of substances which can impair the proper
operation of the system, eg. dirt, air, or the like.
In conventional hydraulic brake systems known to the
applicant, closable bleed openings are provided at high points
in the systems, ie at the upper regions of the slave cylinders.
Closability is provided by screw-threaded bleed nipples adapted
to screw into screw-threaded sockets to close off the bleed
openings.
Bleeding of such systems takes place by opening the
bleed opening, unscrewing the bleed nipple, and by pumplng
hydraulic fluid by means of the piston in the master cylinder,
thereby expelling air from the slave cylinder, and of then
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closing the bleed opening by screwing the bleed nipple home. A
disadvantage of this system of bleeding is that one person is
- needed to operate the master piston to pump hydraulic fluid
~ from the master cylinder through to the slave cylinder, and
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-~ another person is required to watch the bleed opening and to
close it off as soon as air stops issuing from it. The master
cylinder then has to be charged again with hydraulic fluid to
the appropriate level. Bleeding carried out in this fashion is
often not fully effective, because it is not always possible to
, bleed all the air out of such systems in this fashion.
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It is an object of this invention to provide a method
of bleeding hydraulic systems which is more effective than the
~-~ method presently known to the applicant. It is also an object
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to provide suitable apparatus for more effective bleeding.
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According to the invention, a method of bleeding an
hydraulic system which comprises a master cylinder and piston
assembly, a slave cylinder and piston assembly having an openable
and closable bleed opening, an hydraulic line connecting the master
cylinder to the slave cylinder for operatively conducting hydraulic
fluid between the cylinders, and a master cylinder reservoir which
has an openable charging opening and which is in fluid flow communi-
cation with the master cylinder, and which includes the steps of
opening the master cylinder reservoir to atmosphere; introducing
a suction conduit into the charging opening of the master cylinder
reservoir and submerging a suction opening in the suction conduit
below the surface of the hydraulic fluid in the master cylinder
reservoir and withdrawing hydraulic fluid via the suction opening
and suction conduit from the master cylinder reservoir while it is
open to atmosphere; of opening the slave cylinder bleed opening
and introducing hydraulic fluid into the system at the slave cylinder
bleed opening to cause flow of hydraulic fluid from the slave cylinder
and along the hydraulic line to the master cylinder and into the
master cylinder reservoir, thereby permitting undissolved air in the
hydraulic system to escape out of the open master cylinder reservoir;
and of closing the slave cylinder bleed opening.
The hydraulic fluid may be withdrawn from the reservoir of
the master cylinder while maintaining the hydraulic fluid in the
master cylinder reservoir at a predetermined level. Liquid withdrawn
from the master cylinder may be introduced again at the slave cylinder.
The introduction of hydraulic fluid may take place for a
period and the method may include the further step, at the end of said
28 period, of applying a suction at the slave cylinder to cause reverse
flow out of the slave cylinder.
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The introduction of a hydraulic fluid at the slcive cylinder may be
preceded by a step of applying a suction for a period of short duration
at the slave cylinder. The duration of the Suctionperiod may be ten
seconds at the most. The period during which hydraulic fluid is
introduced into the cylinder may be of adjustable duration. The step
of introducing hydraulic fluid into the system and the step of apply-
ing suction may take place in cyclic sequence automatically. The
suction step and step of introducing hydraulic fluid into the slave
cylinder may take place via separate flow paths communicating at the
slave cylinder.
Further according to the invention, apparatus for bleeding
an hydraulic system which hydraulic system includes a master cylinder
and piston assembly, a slave cylinder and piston assembly having an
openable and closable bleed opening, an hydraulic line connecting the
master cylinder to the slave cylinder for operatively conducting
hydraulic fluid between the cylinders, and a master cylinder reservoir
which has an openable and closable charging opening and which is in
fluid flow communication with the master cylinder, the apparatus for
performing the ~leeding comprising hydraulic fluid suction means which
includes a suction tube adapted to enter the charging opening of the
master cylinder reservoir and which is adapted for drawing hydraulic
fluid from the master cylinder reservoir, via a suction opening in the
suction tube, the suction opening in use being submersible below the
level of hydraulic fluid in the master cylinder reservoir; and
hydraulic fluid supply means including a hydraulic fluid supply line
having connecting means disconnectably connectable to the slave cylin-
der bleed opening to supply hydraulic fluid under pressure to the slave
28 cylinder.
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The volumetric flow rate of the hydraulic fluid suction
means may be about 1~ to 2 litres per minute and may exceed that
of the hydraulic fluid supply means by about 50%.
The apparatus may include valve means, and valve operating
means for operating the valve means, for closing off the hydraulic
fluid supply under pressure to theslave cylinder, and for
applying suction to the slave cylinder.
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1086356
The apparatus may include valve operating means and
hydraulic fluid supply and suction means for each of a
plurality of slave cylinders, the several valve operating means
for the plurality of slave cylinders being operable d~scretely
in succession.
The invention extends also to apparatus in which the
hydraulic fluid supply means includes a clean hydraulic fluid
reservoir and a pressure pump having its suction connected to
the clean hydraulic fluid reservoir; in which the hydraulic
fluid suction means includes a spent fluid reservoir and a
suction pump having its delivery connected to the spent fluid
reservoir; and in which there is provided at least one
electric motor for driving the pumps.
The apparatus may further include an hydraulic
connector for connecting the hydraulic fluid supply means to
the slave cylinder, the hydraulic connector incorporating a
valve closure member urged to the closed position, the said
closure member being adapted to become unseated when the
hydraulic connector engages with a bleed nipple in the slave
cylinder.
The invention extends still further to the combina-
tion of apparatus as described with a bleed nipple for a slave
cylinder, the bleed nipple being adapted to engage with the
hydraulic connector and to unseat the valve closure member of
the hydraulic connector.
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The invention extends yet further to a bleed nipple
having a bleed passage and a replaceable non-return valve in
its bleed passage. The bleed nipple may have a female screw
thread in its bleed passage to receive the non-return valve.
The invention also extends to a slave cylinder in an
hydraulic system, in which the slave cylinder has a connection
at a high level connected to an hydraulic line from a master
cylinder, and has a bleed nipple as described at a low level.
The invention will now be described in more detail,
by way of example, with reference to the accompanying drawings.
i In the drawings:
,
Figure 1 shows an hydraulic and electrical circuit
diagram of apparatus according to the invention, the apparatus
being shown connected to .the hydraulic brake system of a motor
vehicle;
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Figure 2 shows an hydraulic circuit diagram of an
alternative form of apparatus;
Figure 3 shows an hydraulic circuit diagram of
another alternative form of apparatus;
Figure 4 shows diagrammatically a diagram of
~i hydraulic fluid flow in another e~bodiment of the apparatus
f acciording to the invention;
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Figuxe 5 shows a schematic diagram of the electric
circuitry of apparatus of Figure 4;
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Figure 6 shows a side view of a transportable trolley
incorporating apparatus according to the invention;
Figure 7 shows a bird's eye view of the control panel
of the trolley shown in Figure 6;
.
Figure 8 shows a bleed nipple forming part of the
assembly of Figure 4;
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. Figure 9tshows an hydraulic flow line diagram of yet
' another embodiment of apparatus according to the invention;
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Figure 10 shows an axial section of an hydraulic
connector with connected conduits as used in the embodiment of
Figure 9;
Figure 11 shows a cross section of the conduits at
XI-XI in Figure 10;
Figure 12 shows an electrical circuit diagram (in-
cluding cams and valves) of the embodiment of Figure 9;
Figure 13 shows an oblique view of a cam shaft with a
few cams mounted thereon;
Figure 14 shows a timing diagram OI the operation of
. various parts and of flow along the various passages through
i valves operated by the various cams; and
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1086356
Figure 15 shows diagrammatically a sectional eleva-
tion of a slave cylinder and bleed nipple assembly for a disc
brake according to the invention.
In Figure 1, reference numeral 10 generally indicates
an apparatus having hydraulic fluid supply means and hydraulic
ÇOP.
fluid suction means in the~pres~ure and suction pumps for use
in bleeding the hydraulic brake system of a motor vehicle.
Reference numeral 12 indicates part of a vehicle's brake
system. The brake system includes a master cylinder and piston
assembly 14, a brake pedal 16 for operating the piston of the
assembly 14, and a master cylinder reservoir 18. When the
pedal is released, the reservoir 18 is in fluid flow communi-
cation with the cylinder 14. The reservoir has a filler
opening 20.
The brake system further includes a brake slave
cylinder and piston assembly 22 on each (say) of the four
wheels (only one of which is shown at 24) of the vehicle. The
master cylinder of the master cylinder and piston assembly 14
is connected to the slave cylinder of the slave cylinder and
piston assembly 22 by means of connector 25 and an hydraulic
line 26.
The apparatus 10 includes a trolley which can be moved
around by hand. It comprises hydraulic fluid supply means in
the form of a delivery pump 28. The pump 28 is a self-
priming, pressure regulated vane pump having a suction inlet
28.22, a delivery outlet 28.21 and a pressure relief connection
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28.1. The pump 28 is driven by a 12 volt electric motor 30.
The apparatus rurther comprises hydraulic fluid suction means
in the form of a suction pump which is a peristaltic pump 32
having a suction inlet 32.1 and a delivery outlet 32.2. The
pump 32 is driven by a 12 volt electric motor 34 via a
reduction gearbox 36. Still further, the apparatus comprises
a spent h~draulic fluid reservoir 38 and a clean hydraulic
flu-id reservoir 40.
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- A suction conduit 42 for withdrawing hydraulic fluid
from the master cylinder reservoir 18, and a delivery conduit
44 for introducing hydraulic fluid into the slave cylinder 22
are also provided. The suction conduit 42 comprises a length
: of flexible tubing 42.1 having at its end a suction connection
i~ in the form of a hooked piece of rigid tubing 42.2. The tubing
42.2 is connected to the tubing 42.1 via a stop cock 46. An
, opening in the tubing 42.2 is arranged to lie at a certain
level in the master cylinder reservoir to maintain a certin
s level of fluid therein.
~ The delivery conduit also comprises a length of
; . flexible tubing 44.1 having at its end a delivery connection in
the form of a length of rigid tubing 44.2. The rigid tubing
44.2 is connected to the flexible tubing via a stop cock 48.
The rigid tubing 44.2 can be connected to the slave cylinder 22
~ by means of a screw-on coupling 50. For this purpose, the
:~ slave cylinder is provided with a nipple (See Figure 8) having
a passage in which there is a non~return valve permitting f low
of hydraulic fluid into the slave cylinder.
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~086356
The suction conduit 42 leads to the suction inlet
32.1 of the peristaltic pump 32. The delivery outlet 32.2 of
the peristaltic pump 32 is ~~onnected to a ~i-directional valve
52 whereby the delivery of the pump 32 can be connected either
to the spent fluid reservoir 38 via conduit 54, or to the
clean fluid reservoir 40 via conduit 56.
The delivery outlet 28.21 of the pump 28 is connected
to the delivery connection 44 via a regulating valve 58. Down-
stream of the valve 58 there is provided a pressure gauge 60.
The suction inlet 28.22 of the pump 28 is connected
via a filter 62 to the clean fluid reservoir 40.
.
The pressure relief connection 28.1 is connected to
the clean fluid reservoir 40 via a T-junction in the conduit
56.
Each reservoir 38, 40 is provided with an overflow
64, 66 respectively. In addition, the spent fluid reservoir 38
is provided with a drainage outlet 68 having a stop cock 70.
The clean fluid reservoir 40 is provided in addition with a
breather 41 which is connected to atmosphere via a silica gel
filter 41.1.
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The unit 10 also comprises a chargeable 12 volt
battery 72 and a battery charger 74 for charging the battery
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'10863S6
from a 220 volt ac mains supply. The battery 72 is connected
via a switch 76 to the two motors 30, 34. A voltmeter 78 is
provided to indicate the condition of the battery.
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In use, the hooked end 42.2 of the suction conduit is
hooked into the filler opening 20 of the vehicle's master
cylinder reservoir and the stop cock 46 is opened. Also, the
delivery conduit 44.2 is connected to the slave cylinder of one
of the wheels of the vehicle by means of the screw-on
connection 50 and the valve 48 is opened.
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, The bi-directional valve 52 is positioned for
delivery into the spent fluid reservoir 38 and the unit is then
switched on by ~eans of the switch 76 which sets the pumps 30
and 34 in operation.
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Hydraulic fluid ~s pumped from the clean fluid
reservoir 40 by means of the pump 28 and via the conduit 44
into the hydraulic system 12. The hydraulic fluid thus pumped
into the system displaces contaminated hydraulic fluid already
in the system. Such contaminated hydraulic fluid is hereinafter
referred to as spent hydraulic fluid, and may be contaminated
by air bubbles, dirt, and other impurities. The flow of fluid
takes place via the line 26 in the direction 80 to the master
cylinder and thence into the master cylinder reservoir l8.
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At the same time, spent hydraulic fluid is drawn from
the master cylinder reservoir 18 via the connection 42 by means
of the peristaltic pump 32. This fluid is pumped via the bi-
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directional valve 52 and the conduit 54 into the spent fluid
reservoir 38.
This process is continued for approximately half a
minute, or until clear hydraulic fluid appears in the master
cylinder reservoir 18. Then after a while until the line 42
has been cleared of spent fluid, the valve 52 is positioned to
deliver into conduit 56 whereupon hydraulic fluid drawn from
the master cylinder reservoir 18 will be pumped towards the
clean fluid reservoir 40 via the conduit 56. The pumps are now
allowed to run for approximately one minute, or until no more
air bubbles appear in the master cylinder reservoir 18.
The rate of flow of hydraulic fluid pumped into the
system is controlled by adjusting the regulating valve 58.
~ After having run for a minute or so, the pump is
: stopped, the stop cock 48 closed and the connector 44.2
unscrewed from the slave cylinder 22. Thereafter, the other
wheels of the vehicle are each treated in the same manner to
complete the bleeding of the brake system.
,
When the bleeding has been completed, the connector
4g.2 is unscrewed and the tube 42.2 taken out of the master
, cylinder reservoir after the valves 48 and 46 have been closed.
The pipes 42 and 44 are then stowed away on the trolley.
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1086356
In the variation shown in Figure 2, the delivery pump
28 is dispensed with by placing the clean fluid reservoir at a
high level to be able to make use of the static head. Thereby
the necessary pressure head is obtained to cause introduction
of fluid into the hydraulic system. This may be of use in
permanent installations such as at assembly plants. In
Figure 2 the same reference numerals as in Figure 1 are used
for the same parts.
In the variation shown in ~igure 3, the suction pump
32 is dispensed with by placing the clean fluid reservoir at a
low level, ie lower than the level of the master cylinder
reservoir. Thereby, hydraulic fluid can be withdrawn from the
master cylinder reservoir by a siphoning action. In Figure 3
the same reference numerals as in Figure 1 are used for the
same parts.
.
By way of modification, the apparatus illustrated in
Figure 1 may be prov ded with a solenoid operated cross-over
valve 82 shown in dotted lines in Figure 1. The valve will be
connected in the suction conduit 42 and in the delivery 28.21
o the pump 28 downstream of the regulating valve 58, as shown
in dotted lines at 84 and 86 respectively. In its de-energised
condition the cross-over valve 82 will then permit bleeding to
take place as described above. When the valve 82 is energised,
however, the conduit 44 is connected to the suction pump 32 and
the conduit 42 to the delivery of the delivery pump 28.
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1(~863S6
The valve 82 is provided to permit the reverse flow
of hydraulic fluid out of the slave cylinder for a short while
at the end of a bleeding operation at each wheel. The
applicants have found that, in certain makes of vehicle 7 air
which may be present in the slave cylinders themselves is not
all removed by bleeding according to the method described
above. By reversing the flow for a short while at the end of
a bleeding operation, this air is removed.
The switch 76 will then be replaced by a double pole,
double throw, centre off switch (not shown) whereby the
solenoid may be energised by switching the switch to one of its
positions.
By way of development the apparatus may be provided
with jump connections 88 fed from the pressure pump 28 via
valves 90. These connections 88 are adapted for connection to
jump conduitsfor bleeding an hydraulic system other than an
hydraulic brake system.
Referring now to Figure 4 of the drawings, reference
numeral 10.4 indicates generally the hydraulic fluid flowline
of another embodiment of apparatus according to the invention.
It is a more developed form of the apparatus shown in Figures 1
to 3. Like numbers refer to like parts. In the following
description reference will only be made to the differences
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between the embodiments of Figures 1 to 3 on the one hand and
the emboaiment of Figures 4 to 9 on the other hand.
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The present embodiment comprises an hydraulic fluid
supply line 44 to which is connected a pressure gauge 60 and
which has a connection 44.11 to which a manifold 45 i5 connec-
ted having as many branch supply lines 45.1 as there are slave
cylinders of a vehicle to be served. Usually, the number will
be four only. Each of the supply lines 45.1 will be provided
with a valve 48 and delivery pipe 44.2 whereby flow along any
supply line 45.1 can be controlled. Each supply line 45.1 is
provided with a connection 45.3 to which flexible conduits 45.4
are connectable via connections 45.5. Each flexible conduit
45.4 also has a connection 45.6 for connection to a bleed
nipple 21 of a slave cylinder 22. The slave cylinder 22 has a
connection 25 to which is connected a hydraulic line 26 ~hich
is fed from a master cylinder 14 having a reservoir 18. The
master cylinder 14 has a piston 14.1 which is connected to a
pedal 16.
The connections 45.3 and 45.5 may each have valves
incorporated in them so that when connections are made both
valves become unseated. ~his is to ensure that hydraulic fluid
contained in the various conduits does not drain when the .-,
conduits are disconnected. Likewise, the connections 45.6 and
the bleed nipples 21 have valves which are unseated when
connection is made between a connection 45.6 and a bleed nipple
21. See in this connection the description with reference to
Figures 9 and 11 of the drawings.
The apparatus also comprises a hydraulic fluid with-
drawal line 42.1 having a connecting device 43 to which is
connectable a flexlble withdrawal line 42 having a connecting
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~ID86356
device 43.1 adapted to connect with the connecting device 43.
Each of the connecting devices 43.1 and 43 has a valve incorpo-
rated therein. Both such valves become unseated when
connection is made between the connecting devices 43 and 43.1.
See in this connection also the description with reference to
Figures 9 and 11 of the drawings.
The suction end of the withdrawal line 42 has a
relatively stiff tube 42.2 which has a longitudinal slot 42.3
near its end. A slidable sleeve 42.4 is provided over the end
of the tube 42.2. The end of the tube 42.2 is insertable into
the reservoir 18 of the master cylinder 14. By adjusting the
height of the sleeve 42.4 relative to the end of the tube 42.2
and allowing the end of the tube 42.2 to rest on the bottom of
the reservoir, the hydraulic fluid can be maintained at a
I -desired level 18.1 in operation while hydraulic fluid is being
fed into the hydraulic system via the slave cylinder 22, and
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while hydraulic fluid is being withdrawn from the hydraulic
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system via the slot 42.3 in the end of the tube 4æ~-. The
' arrangement is such that hydraulic fluid is withdrawn from the
reservoir as long as the hydraulic fluid covers the exposed
' portion of the slot 42.3 completely. As soon as the level of
the hydraulic fluid drops below the sleeve 42.4 then a portion
, of the slot 42.3 becomes exposed, thereby permitting air to
` enter the suction tube 42.2 and thereby preventing the level of
,' the hydraulic fluid dropping below the level 18.1. In this
way, hydraulic fluid which would otherwise have gone to waste
, by overflowing the reservoir 18, i~s now recovered and does not
, go to was~e.
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1~86356
Flow of hydraulic fluid along the hydraulic supply
line 44 and the suction line 42.1 is conveniently controlled by
a control valve 59.
.
A suction filter or strainer, or both, 51 is
connected in the suction line 42.1 so as to remove such
impurities as could damage or affect the operation of the
suction pump 32. The suction line 42.1, or the delivery line
32.2, incorporates a transparent portion so that the purity of
the hydraulic fluid flowing therethrough can be judged.
Depending upon the nature of the fluid, the position of the
valve 52 can be regulated. For clean fluid, the valve 52 will
be connected to the line 56. However, when the fluld is dirty
the valve S2 will be positioned to deliver into the line 54.
, .
Referring now to Figure 5 of the drawings, reference 5
numeral 100 indicates generally the electric circuit diagram of
the apparatus according to Figure 4 of the invention. It
comprises a suction pump motor 34, a pressure pump motor 30 fed
via lines 106 from a battery 72. Voltage supplied by the
battery is indicated by volt meter 78. The illumination for
the volt meter 78 is supplied by the light 112. The illumin-
atlon for the pressure gauges 60 and 75 are provided by the
lights 114 and 116 respectively. The various parts of the
circuit are energised via lines 106 from the battery 72 via the
double-pole double-throw switch 118. When the pole 118.1 is
making contact with the contact 118.2, then the circuit is
energised. When the pole 118.3 co`ntacts the contact 118.4,
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then the relay coil 120 is energised. The coil 120 belng
enexgised, opens contacts 122 and prevents the battery charger
74 being energised while current is being drawn from the
battery 72. The battery charger 74 is energised via lines 126
from ordinary AC supply. The high voltage AC circuit is
protected by a fuse 128. The battery charger has a pilot light
130 to indicate when it is energised. The battery charger
itself comprises a transformer rectifier unit, details of which
are not shown. The output of the battery charger is connected
via lines 132 and fuse 134 to the battery 72. The contacts 122
are normally closed unoperated and only open when the coil 120
is energised.
If the battery 72 has become discharged and does not
have sufficient charge to operate the various motors, then an
emergency supply can be connected to terminals 140 which are
connected via fuse 142 and leads 144 to the leads 106 via the
pole 118.1 when it makes contact with contact 144.1.
.
The electrical and hydrauiic equipment and piping are
all incorporated and brought together in a console from which
the various operations to bleed a hydraulic system, may be
controlled. Thus, the battery, the battery charger, the motors
for the suction and pressure pumps, and the suction and
pressure pumps themselves, and the associated piping and
valves, filters and clean fluid reservoir 40 and spent fluid
reservoir 38, are all brought together. For convenience, they
are brought together in a push-ty~e trolley having a control
panel at its upper end. In this connection reference is made
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to Figures 6 and 7 of the drawings. It comprises an upright
console indicated generally by reference numeral 150. It has a
pair of wheels 152 and legs 154. It can be pushed around by
means of handles 156. The trolley 150 has a control panel 158
on which the various controls are assembled.
Referring now to Figure 7 of the drawings, there are
shown details of the control panel as well of the various con-
necting lines.
Details of a suitable bleed nipple in accordance with
the invention, are shown in Figure 8 of the drawings.
Referr~ing to Figure 8 of the drawings, reference numeral 21
refers generally to a bleed nipple in accordance with the
invention. It has a hexagon formation 180 for engagement by a
~ .
spanner, a screw thread 182 adapted to screw into a threaded
socket in a slave cylinder. It has a seat 184 adapted to
engage sealingly with a non-return valve, generally indicated
by reference numeral 186, engaging wlth the screw-threaded bore
188. The non-return valve 186 is of substantially similar
construction to that used for pneumatic tyres and tubes.
However, there is this difference that the seal 186.1 of the
non-return valve as well as the seat 186.2 of the valve, are of
a resilient material which is resistant to attack by hydraulic
fluid. The nipple is provided further with a screw thread or
other suitable connection 190 for engaging with the connection
45.6 of the flexible supply lines 45.4+ The closure member
186.3 of the non-return valve 186~becomes unseated when the
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connection 45.6 engages with the screw thread 190 (see Figure
10). The valve closure member 45.61 abuts against the end
186.31 of the closure member 186.3, resulting in both closure
members being unseated. A removable dust cap 192 engaging with
the screw thread 190 is also provided.
In operation, for the bleeding of the hydraulic brake
system of a vehicle, the trolley 150 is pushed so that it is
near to the vehicle. Thereupon, four conduits 45.4 are
connected to the connections 45.3 and 50 of the various wheels.
There will therefore be four conduits 45.4 interconnecting the
console 150 to the four wheels of the vehicle. Upon making the
connections 45.6 and 21, the non-return valves built into the
connection pieces, become unseated. The passages in them are
thereby placed in communication with each other. The flexible
conduits 45.4 may form more or less a permanent part of the
apparatus but may be disconnected at 45.~ from the connections
45.3.
Thereupon the piping 42.2 is inserted into the reser-
voir 18 of the master cylinder 14. The sleeve 42.4 is adjusted
to a position to ensure that when hydraulic fluid is pumped
into the system, it will be drawn off at a sufficient rate by ~-
the suction pump so that the level will not rise above a -
reasonable level in the reservoir, eg at level 18.1 as
indicated in Figure 4 of the drawings. Thereupon the motors
for the suction and pressure pumps are energised by closing the
switch 118. This causes clean hy~raulic fluid to be forced
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6356
along the supply line 44 and into the manifold 45. The
appropriate valve 48 is opened and the fluid then flows into
the slave cylinder 22 via the flexible conduit 45.4.
Hydraulic fluid in the slave cylinder 22 thereby becomes
displaced into the reservoir 18 of the master cylinder 14,
However, hydraulic fluid is being withdrawn from the master
cylinder via the tube 42.2, the level of fluid in the master .
cylinder not dropping below the level 18.1 because of the
position of the sleeve 42.4 over the slot 42.3 in the tube 42.2. -~
The capacity of the suction pump is greater than that
of the supply pump, therefore the level of hydraulic fluid in
the master cylinder will not rise above the level 18,1 and
will therefore not spill over at the master cylinder. As ~.
previously mentioned, the reservoir 40 may be provided with a
breather 41 which is in turn connected to atmosphere via a ~:
silica gel filter 41.1. This is to ensure that the air which
enters into the reservoir 40 is dry and that water vapour
does not eventually condense in the reservoir and cause
problems in charging hydraulic fluid lines.
A reservoir capacity of about 5 liters has been found
to be adequate for a portable apparatus. However, if a
permanent installation is contemplated then a clean fluid
reservoir 40 may have many times that capacity.
While the fluid flowing in the suction line 42,1 and
in the suction pump delivery line 32.2 is dirty, then the valve
52 is in such a position that the dirty fluid is discharged
along the line 54 to the spent fluid reservoir 38 or directly
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to drain via line 68. However, as soon as the fluid is seen to
be clean in the transparent flowline, the position of the valve
52 is changed so that the clean fluid is returned via line 56
to the clean fluid reservoir 40.
The slave cylinder 22 shown in Figure 4, is shown as
used conventionally in hydraulic brake systems. In other words,
the bleed connection 21 is provided at the top of the cylinder.
It has been found with such slave cylinders that it is still
possible to have a smalle bubble of air entrapped as at 22.l
(see Figure 4) even after clean hydraulic fluid has been
flowing through the slave cylinder. In such circumstances it
ha been found that the bubble 22.l can be withdrawn from the
slave cylinder by merely causing hydraulic fluid to flow in a
return direction along the conduits 45.4. This is done by
changing the position of the four-way valve 59, so that suction
is applied at the connection 21 for a few seconds merely.
...
.
As the bleeding of the slave cylinder 24 is completed,
so the appropriate valve 48 is closed and the next valve 48 for
the next slave cylinder is opened. In this way the various
slave cylinders may be bled in succession by operating the
appropriate valves in the appropriate sequence.
By way of development, a more sophisticated arrange-
ment may be made by having the various valves 48 of the push-
button type arrangement, operable by a cam or cams on a spindle
so that in different positions of the cam about its axis,
different valves 48 will be closed and only a single valve will
be open at any one time. In this regard reference is made to
Figures 9 to 14 of the drawings.
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Reference numeral 200 refers ~enerally to another
embodiment of the invention having four sets of twin conduits
45.41, 45.42 terminating in four hydraulic connectors 45.6 (see
Figures lO and 11 for details). For purposes of identification
the connectors 45.6 are marked A,B,C,D. A connector is
provided for each wheel of a vehicle. The twin conduits are
connected ~ia connectors 45.3 to pairs of valves arranged in
two banks 48.1 and 48.2. The bank of valves 48.1 are connected
in parallel to the delivery 44 of the pressure pump 28. The
bank of valves 48.2 are connected in~parallel to the suction
conduit 42.1 of the suction pump 32.
The banks of valves 48.1 and 48.2 are cam operated as
will be more fully explained hereafter. The flow of fluid
along conduit 42 from the master cylinder reservoir is con-
trolled by a manually operable valve 43.1, and by a valve
controlled by a clean fluid sensor ~4}~7 and by a cam operated
valve 43.3. The clean fluid sensor may be in the form of a
photo-electric cell responsive to light rays of sufficient
intensity being able to pass through the fluid.
The bank of valves 48.1 controls the flow of
hydraulic fluid along conduits lA, 2B, 3C, and 4D. Likewise
the bank of valves 48.2 control the suction in conduits Aa, Bb,
Cc, Dd.
The electrical circuitry and cams of the apparatus
are shown in Figure 12. Details ~f cams are shown in Figure
13, and the timing of the operation of various parts is shown
in Figure 14.
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The embodiment 200 has terminals 201 for energizingfrom a battery, say the battery of the vehicle whose brakes are
being bled. Alternatively, the apparatus may be energized via
AC terminals 202 and via switch 202.1 and transformer 203 and
fullwave rectifier 204. The apparatus also includes a trickle
charger 205 for trickle charging a battery.
The apparatus comprises a six pole three position
selector switch 206. In Figure 12 it is shown in the off
position. When in the upward position it is in the 'automatic
position 'Au' and when down, it is in the 'manual' position
'Ma'. The circuit also has a main switch 207, and is protected
by a fuse 208. Besides including solenoid valves 90.1 serving
the purpose of valves 90 in Figures 1 and 4 of the drawings,
the circuit also includes the pressure and suction pump motors
30 and 34.
,' ~
The circuit also includes a cam motor 209 controlled
by variable speed control 209.1 and gearbox 210 driving a
camshaft 211 on which is mounted a series of cams CI, CII to
CX. The cam CI has four lobes and operates valve 43.3 (see
also Figures 9, 13 and 14). Cam II operates cycle termination
switch 212 which stops operation of the machine when it is
operating on automatic. The cams CIII, CV, CVII and CIX each -
have two lobes and are adapted to open the suction lines Aa,
Bb, Cc, Dd at the beginning and end of a bleeding cycle for
each of wheels WI,.WII, WIII and WIV (see Figures 9, 13 and 14)
in succession. These cams operate the bank of valves 48.2.
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The cams CIV, CVI, CVIII and CX each have one lobe and are
adapted to open the pressure lines 1~, 2B, 3C, 4D ~Figures9 and
14~ at the same time that the suction line through valve 43.3
is open (see Figures 9 and 14).
'
The circuit further comprises a push button start
` switch 213, a relay coil 214 adapted to hold itself energized
over lower contacts 214.1. In Figure 12 contacts 214.1 are shown
in the unoperated position. The circuit also includes a cycle
termination indicator in the form of a light 215.
. - . ` ':
When the selector switch is in the manual position
'Ma' (see Figure 12) the main switch is switched on and the
` push button switch 213 is closed. The relay coil 214 becomes
energized and holds itself energized over the lower contacts
214.1. At the same time the pressure and suction pump motors
30 and 34 are energized as well as the two solenoid valves
90.1. The apparatus can then be used for ~leeding any other
hydraulic system by making use of jump connections 88 (see
Pigures 1 and 4 above). On manual, the cam motor 209 is not
,energized.
For automatic operation the varlous connectors 45.6
are connected to the nipples 21 at A,BjC,~ of the four wheels
WI, WII, WIII and WIV. (See Figures 9, 10 and 11).
When the selector switch 206 is on automatic 'Au'
then the cam motor becomes energized when the main switch 207
and start switch 213 are closed. In addition those portions
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of the apparatus which ~Jere energized under 'Manual' are also
energized. The cycle of operations is started by holding the
start button 213 for a few seconds to ensure that cam CII is no
longer operating the cycle termination switch 212 and that
switch 212 is in its unoperated closed position shown in Figure
12.
The cam shaft 211 starts rotating and the pressure
and suction pumps 28 and 32 are connected in timed sequence via
the valve 43.3 and the banks of valves 48.1, and 48.2 for the
various wheels forming part of the system to be bled. The
connections ta~e place according to the timing and sequence as
shown in Figure 14.
Further details are set out in the table below.
Wheel Wheel Wheel Wheel
WI WI I WI I I WIV
Energized A B C D
Closed 1-4 1-4 1-4 1-4
Phase 1 Open a b c d
Closed bcd acd abd abc
Closed 43.3 . 43.3 43 3 43 3
.
Open 1 2 3 4
Phase 2 Closed 234 134 124 123
Closed abcd abcd abcd abcd
Open 43.3 43.3 43.3 43.3
Closed 1-4 1-4 1-4 1-4
Phase 3 Open a b c d
Closed bcd acd abd abc
Closed 43.3 43.3 43.3 43.3
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One revolution of the cam shaft constitutes one
compl~te cycle. At the end of the cycle cam CII operates the
cycle termination switch 212 thereby de-energizing the
apparatus including relay coil 214. The contacts 214.1 return
to their unoperated upper position thereby energizing cycle
termination indicator light 215. This indicates that bleeding
on a particular vehicle has been completed and that the
: CO~N6C.~DR
hydraulic ~#U~ffK~Y~ 45.6 at A,B,C,D may be disconnected, and
reconnected to the next vehicle for the next cycle of operations.
,- The initial short suction phase applied to the
conduit in phase 1 for a few seconds, is intended to remove
dust or other dirt at the bleed nipple inlet. This is to
prevent such dust or dirt being charged into the hydraulic
~- system. Then follows phase 2, introducing hydraulic fluid into
li
the slave cylinder for about a minute or more. Finally there
is another short suction phase for a few seconds.
, .
- The duration of the cycle is chosen such that with
the pump capacities of the apparatus an hydraulic system can be
adequateIy bled. For large systems the length of cycle can be
increased by slowing the cam motor down by means of control
209.1.
The method of bleeding according to the invention can
be carried out particularly successfully where the line leading
from the slave cylinder to the master cylinder is at a higher
level than the introduction of the hydraulic fluid in the slave
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cylinder. Reference is now made to Figure 15 in which there is
shown a slave cylinder assembly 220 in accordance with the
invention.
This assembly comprises a pair of slave cylinders 222
and 224 interconnected via a channel 226. The cylinders have
pistons 228 and 230 arranged on either side of a disc 232. In
,~ accordance with conventional practice, the master cylinder
hydraulic line connects with the cylinder 224 at about the line
224.1: and a bleed screw nipple is provided at the end of the
branch passage 226.1. In accordance with the invention
however, (shown in Figure 15) the master cylinder hydraulic
line connects with the branch passage 226.1, and bleed screws
or bleed nipples 21 in accordance with the invention are
provided at a low level in each of the cylinders 222 and 224.
, j . :
Hence, in accordance with this invention, it is
better to have the bleed nipple of a slave cylinder at a low
level rather than at a high level as has been the practice
heretofore. Accordingly, this invention has a slave cylinder
having means for connecting it operatively to a master
cylinder, and having a bleed nipple at a low level leading into
the slave cylinder, the bleed nipple having means for con-
nection to a hydraulic fluid supply capable of causing flow of
hydraulic fluid through the slave cylinder to the master
cylinder. The slave cylinder connection leading to the master
cylinder may be at a high level.
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