Note: Descriptions are shown in the official language in which they were submitted.
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BRAKE ACTUATING SYSTEM.
This invention relates to vehicle braking systems
and more particularly concerns fluid actuated braking
systems.
Conventional fluid actuated vehicle braking systems
include a source of fluid under pressure such as a com-
pressor driven by the vehicle prime mover and connected
to and building pressure in a fluid tank. The tank is
connected by a main service line to the brake mechanism,
the line including valve means actuated by the vehicle
driver such as by operating a vehicle brake pedal. The
service line includes means which on release of the pedal
cause the line to be exhausted to atmosphere where the
fluid is gas e.g. air or into a low pressure zone in the
case of the fluid being a liquid e.g. oil.
Many known circuits, especially when incorporated '
in tractor-trailer combinations, include a second service
line known as an emergency line which is supplied with
pressurised fluid from the pressure fluid source of the
main service line and has its own pressurised fluid tank. ~ '
Systems involving main and emergency service lines are
known as two-line systems and are compulsory in many '~
countries.
; Three line systems are sometimes~employed and in
'some countries are obligatory. In su'ch systems a third
service line, sometimes called a "dead man line" is
included having its own source of pressurised fluid
supplying a line with its own valves actuated by action
by the vehicle driver as by application of the vehicle
hand br'ake by the driver, and operable if the main and
emergency circuits are inactive or fail.
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When a driver reverses a vehicle, particularly a large
heavily laden goods carrying vehicle, his rear vision is often
obstructed and he is unable to see an obs-tacle behind his vehicle.
Rigid obstacles such as a loading bay or a wall may be damaged
and also cause damage to the vehicle and where the obstacle is a
human or animal body serious injury or death may result.
Detector devices are known which actuate a warning such as
a horn or light in the driver's cab to alert the driver to apply
the brakes but these suffer from the disadvantage that the
ariverls reaction time may be too long for a collision to be
avoided. Also when the obstacle struck has moved out oE contact
with the detector it then eeases to activate the warning device.
An object of the present invention is to provide a vehicle
braking system in which the aforesaid disadvantages are minimised
or eliminated.
The present invention provides a vehiele braking system
comprising fluid actuated brakes, at least one souree of pres-
surised fluid, at least one service fluid line connecting said
source of pressurised fluid to a brake actuating arrangement, said
brake actuating arrangement serving to apply the brakes in re-
sponse to a change in pressure in said serviee line, the improve-
ment which eomprises the addition of an auxiliary braking system
comprising:
(a) an auxiliary fluid circuit including a fluid control
valve disposed in said service line between said
source of pressurised fluid and said brake actuating
arrangement;
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(b) a detector mounted at the rear of the vehicle and
movable between operative and inoperative positions;
(c) first control means responsive to the position of the
detector and providing an open fluid path in said
auxiliary Eluid circuit when the detector is in its
operative position and obstructing said fluid path
when the detector is in its inoperative position;
(d) second control means independent of said first control
means and responsive to the position a driver-controlled
-reverse selector on the vehicle, said second control
means providing an open fluid path in said auxiliary
circuit when said driver-controlled reverse selector
is in a vehicle-reversinq condition and obstructinq
said fluid path when the selector is not in a vehicle-
reversing condition;
(e) said auxiliary circuit fluid control valve being so
connected that upon operation of said auxiliary circuit
fluid control valve by the first and second control
means, the fluid path in the service line between said
valve and said source of pressurised fluid is obstructed
and the fluid path between said fluid control valve
and said brake actuating arrangement is opened, whereby
said fluid actuated brakes are applied.
Preferably, the auxiliary braking system is arranged to cause
operation of the brakes when the detector is deflected from its
inoperative position and the driver-controlled reverse selector
is in the vehicle-reversing condition, and to release said
operated brakes only when the detector is in said deflected
operative position and the driver-controlled reverse selector
is not in the vehicle-reversing condition.
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In this specification the expression "Eluid service line"
re~ers to one of the fluid lines present in the conventional braking
system, e.g. the principal service brake line operated by the
driver's foot ~rake and the emergency line in a two-line system,
In a three-line system it includes the additional emergency line
known as the "dead man line".
Reference is now made to the drawings in which:-
Figure 1 is a perspective view showing diagrammatically therear of a vehicle having a detector bar fitted thereto;
lQ Figure 2 is a simplified circuit diagram of a braking system
of an articulated vehicle comprising a tractor unit and trailer
unit with auxiliary braking means according to the invention; and
Figure 3 is a simplified circuit diagram of a braking system
showing modification to the system shown in Figure 2.
The diagram shown in Figure 2 shows the application of the
present invention to a conventional three-line vehicle braking sys=
tem. The diagram in Figure 2 shows the basic tractor layout to
the right of the vertical line X - X and the trailer layout to
the left of the line X - X. It will be apparent that these cir-
cuits could be modified to a two-line system and that such
circuits may be applied to a tractor-trailer, a tractor semi-
trailer unit or a single unit.
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The systems described, with reference to the draw-
ings, are air-brake systems which operate with air unde~
an elevated pressure but they may also be operated with
air under reduced pressure, i.e. a vacuum system. The
invention is also applicable to equivalent hydraulic
systems.
Figure 1 of the drawings shows the rear of a vehicle
fitted with one form of detector according to the invention.
The detector is in the form of a detector bar 10 which is
pivoted at 11 and 12 to actuate a control valve 13 fixed
to the vehicle. The detector bar 10 may ~e provided with
means such as spring means (not shown) to blas it
outwardly from the rear of the vehicle into its inopera-
tive position. Limiting means (not shown) may also be
provided to limit the amount of outward movement of the
bar 10.
The detector bar 10 can pivot towards the rear of -
,the vehicle about the pivots 11 and 12 from the inoper- -
ive position to an operative position in which it opens
the control valve 13 which is normally closed and which is
mounted on a bracket 14 rigid with the vehicle. The
valve 13 shown is a mechanically actuated valve but this
may be replaced by an electrical switch which completes
at electrical circuit to operate an electrically operated
control valve such as a solenoid valve~
The biass,inq of the bar should be such as to
achieve the desired sensitivity so that a relatively small
contact pressure will pivot the bar to its operative ',
position and actuate the control valve 13 or switch. ,
In Figures 2 and 3 of the drawings only the trailer
brake operation is shown for simplicity,'the tractor
brakes being operated on a similar principle including
where the system is applied to a tractor only.
The system is supplied with air under pressure to
an air line from a compressor driven by the tractor's
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prime mover in a conventional manner. For simplicity
many conventional integers such as air dryers, variable
load valves responsive to the load on -the road wheel
axles, and relays are omitted from the drawings but will
usually be employed in a conventional manner. Single
circuit protection valves may be fitted close to each
of the reservoirs so that should one service line fail,
the feed to the other line will continue to be maintained
to enable the brake system to function.
Conventionally, a tractor unit comprises a main
air tank M which can supply pressurised air to a line N
under the control of a driver's foot brake pedal T, the
line ~ terminating in a connector whereby it may be
connected by a flexible line to a conventional connector
Nl leading to a corresponding line N2 in the trailer.
This line is the principal service line of the tractor-
trailer.
The conventiona~l tractor unit also comprises an
auxiliary air tank B which is connected via a line P to
a flexible line which m~y be connected to connector P
which leads to a corresponding line P2 in the trailer.
This line is the so-called "dead man line". The auxiliary
air tank B is also connected via the line R and a flexible
connector Rl which leads to a corresponding line R2 in
the trailer. This is the emergency line.
In preferred brake actuating systems of the
invention said auxiliary air tank B is also connected to
a valve A which is activated by the driver controlled
reverse selector of the vehicle (not shown). This selector
will usually be a reverse gear selector in a gear-box
of the manual or automatic type. The valve A is arranged
so that it is in the open position when the reverse sel-
ector is in the vehicle reversing condition, the valve
also being provided with an exhaust to atmosphere which
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is opened only when the reverse selector is in a condition
other than a vehicle reverse condition. The valve A is
connected to a line S which can be connec-ted with a
flexible line to connec-tor Sl which leads to an auxiliary
air line S2 on the trailer. This line is part of the
auxiliary braking means according to the invention.
The trailer is provided with a brake chamber
associated with each wheel G, H, I and J and for normal
bra~ing under driver control these are connected to a
relay emergency valve F which, in turn, is connected to
a trailer air tank K. Thus, when the driver operates
the foot brake pedal T, pressure is applied via lines N,
Nl and N2 to the shuttle valve E and hence the relay
emergency valve F causing the valve to open and pressurised
air is then applied from the tank K to the brake chambers
G, H, I and J causing the vehicle brakes to be actuated.
The line R, Rl and R2 is also connected to the relay
e~ergency valve F and is such that if the pressure of the
air in the auxiliary air tank B does not reach a certain
predetermined level then the relay emergency valve will
be caused to open and permit pressurised air from the tank
R to be connected to the brake chambers G, H, I and J.
Another safety feature which is conventionally incor-
porated in three-line systems is the line P, Pl and P2
which connects the quick release valve L to the auxiliary
air tank B. This is the conventional "dead man line" and
when pressure is applied via the line P, Pl and P2 to the
quick release valve L, then the pressurised air from the
auxiliary air tank B is connected to each of the brake
chambers G, H, I and J.
One auxiliary braking system according to the
present invention shown in Figure 2 utilises the relay
emergency va]ve to cause pressurised fluid to be applied
to the brakes. In this embodiment the line S, Sl and S2
from the valve A is connected to a first control valve C
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which is actuated by a detector bar D movable between an
inoperative position and an operative position when it is
deflected by an object. When the detector bar D is in
the operative position it causes control valve C to open
and thereby connects the line S, Sl and S2 to the line
S3 which applies pressure from the auxiliary air tank B
to the shuttle valve E, caus:ing the line N, Nl and N~
to be shut off and applying pressure to the relay valve F.
This pressure causes the relay valve F to operate and
- 10 apply pressure from the air tank K to the brake chambers
G, H, I and J and thus causes a~tuation of the brakes.
The auxiliary braking system described above is
extremely simple to add to the existing braking system
as it merely comprises the valve A to be operated by the
reverse selector of the vehicle, the lines S, Sl, S2 and
S3, the control valve C and the shuttle valve E. It will
be seen that the addition of this auxiliary system in
no way a~fects the ex'isting braking system as it is merely
necessary to insert the shuttle valve E in the connection
between the line N2 and the relay emergency valve F.
The operation of the auxiliary braking system will
now be described.
When the driver wishes to reverse the vehicle it
is necessary for him to select a vehicle reversing con-
dition of the reverse selector. This opens the valve Acausing pressure to be applied along the line S, Sl and
S2 from the air tank B to the control valve C. The driver
will then be able to reverse the vehicle normally until
the detector bar D strikes an object and is deflected
thereby. The detector bar D will move towards the vehicle
as a result of the impact to open the control valve C
thereby connecting the pressurised air in line S2 to line
S3 and the shuttle valve E causing xelay emergency valve
F to actuate the vehicle brakes. It will then be impossible ~
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for the driver to reverse any further, and experience
has shown that a fully laden articulated vehicle will
stop from normal reversing speed in about three inches.
If the driver now selects a condition other than thereverse
condition of the selector, the valve A will be closed and
the line S connected to atmosphere by the exhaust Al
so that the pressure applied to the shuttle valve E and
relay valve F will be released and the driver can then
move the vehicle.
It will be appreciated however, that this will only
occur where the detector D has remained in its operative
position to maintain the control valve C in the open
position, i.e. where the detector has contacted an object
immovable under the force applied by t~e detector D.
Where the detector D contacts a movable object such as a
person, then it is possible that the person will cease
to apply pressure to the detector D, for example, the
person may fall and the control valve C will then be
closed as the detector moves to its inoperative position.
It will be seen that in this situation, it will not
be possible for the driver to move the vehicle in any
direction since the brakes will be applied via the relay
emergency valve F, but the closing of the control valve C
will prevent exhaustion of the pressurised air in the
line S3 to the exhaust Al. In conse~uence, the driver
will not be able to move the vehicle either forwards or
backwards.
In order for him to move the vehicle it will be
necessary for the detector D to be moved again in order
to open the control valve C causing the air to exhaust
the pressurised air to atmosphere. In normal circum-
stances this will involve the driver in walking to the
rear of the vehicle in order to effect the necessary
deflection of the detector D and he will then have the
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opportunity to inspect the o~ject which has been struck.
It is believed that this is a considerable safety factor
in that i~ the detector bar cloes strike a movable object,
the driver must leave his vehicle and go round to the
rear to deflect the detector bar before he can move the
vehicle either forwards or backwards.
An alternative embodiment of the invention is
shown in dashed lines`in Figure 2. This embodiment makes
use of the "dead-man" line in a conventional three-line
system.
In this embodiment the control valve C is not
connected to the shuttle valve E by the line S3 but is
connected to a quick release valve L by a line U which
is incorporated in the '1dead-man" P, Pl and P2. The
operation of the quick release valve L will cause the
pressure from the auxiliary air tank B to be applied to
the brakes causing braking of the vehicle. This system
has the disadvantage with respect to the system described
above, in that it is slower to operate by virtue of the
fact that the air line is connected to a remote air tank
B and ~uicker operation can be obtained by connection to
the trailer air tank K. The arrangement will still
require the opening of the detector control valve C in
order to release the brakes by releasing the pressure
through the exhaust to atmosphere on valve A.
The exhaust to atmosphere need not be made through
the valve A but could be made in a conventional manner,
for example through the quick release valve. Such an
arrangement would pro~ide for actuation of the bra~es
when the detector is deflected to its operative position
whilst the vehicle is reversing and the brakes would
remain applied until the driver selects a condition of
the reverse selector other than reverse or the detector
moves to its inoperative position. When the exhaust
to at~osphere is provlded on the side of the control
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valve C which is connected to the source of pressurised
air (e.g. in the line S, Sl, S2 or valve A in this
embodiment) and there is no provision for exhausting the
air line (S3 in this embodiment) to the valve which causes
actuation of the brakes then it will be necessary for
control valve C to be open ~or exhausting to take place
and the brakes to be released.
The provision of the exhaust in the valve assoc-
iated with the reverse selector of the vehicle also
ensures that the brakes can be released only when the
selector is in a condition other than the vehicle revers-
ing condition, but it will be apparent that i~ this
feature is not required the exhaust could be located in
a different part of the circuit.
The embodiment described above can, of course, be
modified to utilise another quick release valve in the
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emergency line if such ~a~e is provided.
A further alternative form of the invention is
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shown in Figure 3. This arrangement is applicable to
both two-line and three-line systems and utilises the
emergency line R2 and the relay emergency valve F of an
existing braking system.
Figure 3 the designation of the relevant components
is the same as shown in Figure 2, with the exception that
an additional valve V is inserted in the line R2 to the
relay emergency valve F. The relay emergency valve F is
connected to the main service line N2 and the vehicle
brakes G, H, I and J as in Figure 2.
The emergency line R2 is normally maintained under
pressure and the brakes are operated by means of the
relay emergency valve F when there is a drop in pressure
in the line R2. The valve V is a three-way pilot-oper-
ated valve which is connected to the line S3 from the
first control valve C, as shown in Figure 2.
When the detector D is moved to its operative
position, it causes pressure to be-applied via the
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line S, Sl, S2 and S3 to the three-way pilot operated
valve V and this valve causes the inlet of air at V1
to be interrupted and the outlet at V2 to be connected
to an exhaust V3. Thus the pressure in the line R2
to the relay emergency valve F is reduced to atmospheric
pressure and the relay emergency valve F causes pressur-
ised air to be applied to the brakes.
It will be seen that, as with the arrangements of
Figure 2, the valve V will remain in this condition even
if the detector D returns to its inoperative position,
as the line S3 can be exhausted to atmosphere only by
way o the lines S , S2 and S and the valves C and A.
It is, of course, possible to provide more than one
detector at the rear of a vehicle and also one or more
control valves. It is particularly convenient to use
a single detector which extends over the width of the
rear of the vehicle as shown in Figure 1 but two or more
such detectors coula be used if desired.
A convenient arrangement is to provide one or more
additional detectors which is or are forward of a rear
detector. This provides -an additional safety factor in
that, for example, where a human or animal moves beneath
the vehicle forward of the detector at the rear of the
vehicle then the brakes can be applied by deflection of
an additional detector. Such an additional detector
or detectors are conveniently associated with flap
members disposed to the rear of the vehicle road wheels.
The driver-controlled reverse selector of the
vehicle wili usually be the reverse gear of a manual or
automatic gear-box but it can be any reverse selector
mechanism. The operation of the valve may be effected
mechanically by the gear lever or a member associated
therewith, or it may be effected by a member associated
with any part of the mechanism for driving the vehicle
in reverse. Alternatively, the member may actuate an
electrical switch and the valve may be an electrically
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operated valve, such as a solenoid valve.
Whilst in the foregoing description the first
and second control valves are described as mechani-
cally operated valves it will be apparent that, if
desired, either or both valves can be an electrically
operated valve, such as a solenoid valve, operated by
an electrical circuit actuated by a switch controlled
by the detector and the reverse selector of the vehicle
respectively.
The provision of an auxiliary braking system in
ac~ordance with the present invention is relatively
simple and can readily be installed in new vehicles as
well as into existing vehicles.
The system has considerable advantage over
existing systems in that the operation of the brakes ,
in response to deflection of the detector occurs in-
dependently of any driver action other than placing
the reverse selector in the vehicle reversing condition.
When the reverse selector is in a condition other than
the vehi~le reversing condition the detector is inoper-
ative and consequently it will not cause application
of the vehicle brakes for example when a following
vehicle collides with the detector.
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