Note: Descriptions are shown in the official language in which they were submitted.
Anti-Jackknifing Device for Articulated Road Vehicles
The invention relates to anti-jackknifing devices for
articulated road vehicles, especially tractor-trailer
combi~ations coupled together by so-called fi~th wheei devices.
Various proposals have been made to prevent jackknifing of
articulated vehicles. For example, U.S. patent specification
number 4,241,934, dated December 30, 1980, discloses a coupling
device in which a pin mounted on a plate hinged to the front of
the trailer is lowered into an arcuate slot in a structure fixed
to the tractor frame. The slot limits movement of the pin and
hence the extent to which the trailer can pivot relative to the
tractor. The plate is lowered and raised by means of an
hydraulic ram attached to the front wall of the trailer. U.S.
patent specification number 3,733,090, dated May 15, 1973,
discloRes a pair of pins mounted on the fifkh wheel cooperating
with spring-loaded bumpers mounted on the trailer to limit the
maximum angular relationshlp of the tractor and trailer. U.S.
patent specification number 4,204,700, dated May 27, 1980,
discloses a pair of pneumatic cylinders mounted on the trailer
and cooperating with the fifth whesl assembly mounted on the
tractor. Mounting pneumatic cylinders or dampers on the trailer,
as taught by these prior proposals, is an expensive way to equip
an entire fleet since there are perhaps four times as many
trail ers as tractors.
An antt-jackknifing coupling device which confines the
modifications primar1ly to the tractor is disclosed in U.S.
patent specification number 3,~50,449, dated November 26, 1974,
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which discloses a fluid piston-and-cylinder link fastened at one
end to the tractor, a~ a point spaced well forward of the fifth
wheel assembly, and at the other end to the upper plate of the
fifth wheel, so that pivoting of the tractor and trailer from the
aligne~d position causes contraction of the fluid piston-and-
cylinder link. This still requires a piston extending a
significant distance from the fifth wheel assembly to a point
near the cab of the tractor, which would not facilitate movement
of the fifth wheel assembly longitudinally of the tractor to
optimize the load distribution between the front and rear wheels
of the tractor. Also, the piston-and-cylinder device would
encroach upon useful space behind the cab of the tractor.
An object of the present invention is to provide an anti-
jackknifing coupling device which is relatively economical to
install on a fleet of articulated vehicles.
Another object of the invention i8 to provide an anti-
jackknifing coupling device which controls rotational movement
of the articulated units while permitting movement of the
coupling position to and fro along the tractor.
According to one aspect of the present invention an anti-
jackknifing coupling device for an articulated vehicle comprising
a tractor-trailer combination, comprises a base member adapted
for mounting upon said tractor. A turntable member is rotatably
mounted upon said base member, and a trailer support member
adapted to releasably couple the trailer is supported upon, and
rotatable with, the turntable member. At least one piston-and-
cylinder device 1s connected at its one end to the trailer
support member of the turntable member and at its other end to
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the base member, the arrangement being such that relative
rotation of the turntable member and the base member changes the
length of the piston-and-cylinder device. Control means is
operable to control said piston-and-cylinder means to inhibit
pivoting of said trailer support member in at least one
direction.
The piston-and-cylinder device may extend substantially
diametrically across the turntable member.
The trailer support member may be pivotal relative to the
turntable member about a horizontal axis and the piston-and-
cylinder device may then extend in the same plane as the pivot
axis i.e. laterally of the tractor. This reduces wear and tear
on the piston-and-cylinder device due to tilting of the trailer
support member as the vehicle traverses bumps or other
undulations.
~dvantageously, the cylinder may be connected to an
accumulator, conven~ently a pneumatic accumulator, and a valve,
operable by the tractor's brakes. When the brakes are applied,
the valve closes, preventing contraction of the piston and
cylinder, and forcing the fluid to enter the accumulator. The
accumulator acts as a shock absorber, storing fluid resiliently
and damping the stoppage of the piston. When the vehicle starts
to straighten, the accumulator will return the fluid to the
cy1inder under force, assisting the straightening operation.
Flow restrictor means may be provided in a bypass to provide
some resistance to piston movement when the anti-jackknifing
device i8 not employed, i.e. the valve is open Different degrees
of resistance for the flow restrictor means may be selected by
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the driver and/or automatically to suit road or traffic
conditions. Preferably the flow restrictor can be set to provide
no restriction so that, with the valve open, fluid flow is not
i mpede!d .
The trailer support member7 i.e. the so-called fifth wheel,
may have lock;ng means, for example a pin urged upwards to engage
in a hole in the underside of the trailer.
In this specification the term "trailer" is used to embrace
a vehicle having wheels at its rear only, its front end being
supported by the tractor unit to which it is coupled.
According to a second aspect of the pressnt invention, there
is provided a tractor having an anti-jackkni~ing coupling
according to the aforementioned first aspect.
Figure 1 is a side view of an articulated road vehicle
comprising a tractor and a trai1er;
Fi~ures 2, 3, and 4 are detail plan views of a so-called
"fifth wheel" anti-jackknifing device coupling the tractor and
trailer;
Figure 5 is a section throu~h the fifth wheel device shown
in Figure 2;
Figure 6 corresponds to Figure 1 but shows the tractor and
ifth wheel device to a larger scale; and
Figure 7 illustrates electrical and hydraulic circuits
associated with the fifth wheel device.
~26 Referring to Fi~ure 1, an articulated road vehicle comprises
a tractor 10 and a trailer 12 coupled together by an anti-
jackknifing coupling device 14, usually called a fifth wheel
assembly. The fifth wheel a~sembly 14 is mounted above the rear
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wheels of the tractor lo and the front end of trailer 12 rests
upon a trailer support member in the form of fifth wheel 16.
Referring to Figures 2, 3, 4, and 5, the trailer 12 has a king
pin 17 (Figure 5) which engages in a slot 18 in the trailer
support member 16, so as to allow the trailer 12 to pivot
relative to the tractor 10. The mouth of the slot 18 diverges
outwardly as at 20.
Referring to Figure 5, the fifth wheel 16 is mounted by
means of diametrically spaced trunnion pins 22 and 24,
respectively, upon a turntable 26. Trunnion pins 22 and 24
extend through lugs 28 and 30, respectively, which depend from
fifth wheel 16, and through cooperating lugs 32 and 34,
respectively, upstanding from turntable 26. The trunnions 22 and
24 permit the fifth wheel 16, and hence the trailer 12, to tilt
relative to the turntable 26, and hence the tractor 10, about a
laterally extending axis 36.
Turntable 2~ i8 mounked upon a base member 38 comprising a
flanged portion 40 which, in use, is uppermost and secured by a
central boss 42 to a base plate 44 which is lowermost, in use.
In Figure 5, the base plate 44 is shown secured to longitudinal
frame members 46 and 48 of the tractor 10 by screw threaded studs
BO:and 52, respectively.
As shown more clearly in Figures 2,3,4, and 6, the fifth
wheel 16 has a cylindrical recess 54 housing a plunger 56. When
the bearing plate 58 of a suitable trailer i.e. having a
correaponding hole to receive plunger 55, is resting upon trailer
support plate 16, compressed air applied to cylinder 54 urges
plunger 56 upwards 80 as to engage in the hole in the trailer
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bearing plate 58 and prevent rotation of the fifth wheel 16
relative to the trailer 12. If a trailer 12 without these holes
is coupled, the pins 22 and 24 will not engage the trailer
support plate and the trailer 12 will be allowed to pivot
relat;ve to the fifth wheel 16 in a conventional manner. In the
latter case, the turntable 26 will be prevented from rotating
relative to the tractor 10, as will be explained later.
The compressed air for operating the plunger 56 will be
supplied from the usual compressed air system provided on such
vehicles. To engage the plunger 54, the driver will operate a
switch (not shown), which might be inside the cab or adjacent the
fifth wheel.
It should be appreciated that compressed air is not the only
way of displacing plunger 56. It could be urged upwards
manually, hydraulically or mechanically (e.g. by a lever).
An hydraulic ram device, comprising a piston ~0 and a
cylinder 62, is mounted between the base member flange 40 and the
turntable 26. Specifically the cylinder 62 is pivotally attached
at its free end to a pin 64 upstanding from a raised portion of
the turntable 26 and the piston connecting rod 66 is pivotally
attached to a ptn 68 upstanding from base flange 40. As shown
in Figures 2,3 and 4, rotation of the fifth wheel 16 in either
direction from the straight-ahead position of Figure 2 will cause
foreshortening of the piston-and-cylinder device.
~5 As shown in Figure 7, a one-way valve 70 is coupled by
hydraulic lines 72 and 74, respectiYely, to opposite sides of the
piston 60. An accumulator 78 is coupled to the end of cyl~nder
62 attached to pin 64 and a reservoir 80 i8 coupled at its other
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end. Reservoir 80 compensates for the volume occupied by the
connecting rod 66 of piston 60. A normally open valve 82 and a
variable flow restrictor 84 are connected, in s~ries, between the
cylinder ports to which the accumulator 78 and the reservoir 80
are connected, i.e. between opposite ends of cylinder 62, as a
second bypass.
When the piston 60 is being forced into cylinder 62 by
pivoting of the tractor 10 relative to the trailer 12, the
hydraulic fluid displaced by the piston 60 cannot return by way
of one-way valve 70 and so must enter accumulator 78 and/or
return by way of valve 82 (if open) and the variable flow
restrictor device 84. The valve 82 is electrically operable by
means of a switch 86 on the steering column 88 of the tractor 10.
for purposes of illustration, a second switch 90 is shown
16 attached to the brake pedal 92, thou~h it would more likely be
an hydraulic switch 1n the brake line.
8wttch 90 i8 connected in parallel with switch 86, so valve
82 wi 11 close either when the driver applies the brakes or when
he operates the switch 86 on the steering column 88. When valve
82 closes, movement of piston 76 into cylinder 62 wi 11 be
arrested, since fluid cannot return via one way valve 70. Some
will enter the accumulator 78, until its capacity is reached. The
accumulator 78 will absorb fluid resiliently, acting as a shock
absorber to dampen the stoppage of the movement of the piston and
cylinder. Otherwise the jolt as the piston-and-cylinder device
"locked up" might cause loss of control, especially on slippery
roads.
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Wh~n valve 82 is open, i.e. the brakes are not applied,
fluid can flow via valve 82 and flow restrictor 84 permitting
retraction of the piston 60 from the cylinder 62. The variable
flow restrictor 84 has three possible states, fully open, low
restriction, and high restriction, and is connected to a three-
way selector switch 94 on the dashboard inside the cab. The
driver may operate selector switch 94 to select either high or
low resistance to retraction of the piston-and-cylinder device.
This provides a certain amount of "stiffening" of the articulated
vehicle, even when the anti-jackknifing feature is not employed.
If the driver selects the fully open state, with valve 82
also open, the movement of piston 60 will not be impeded in
either direction. The driver typically will select this
combination when manoeuveriny at low speeds. On the other hand,
there may be occasions when the drlver wlsheQ to 10ck the plston-
and-cylinder device to prevent further plvot1ng of the ~railer
12 and tractor 10 relative to each other, in which case he may
close valve 82, i.e. by operating switch 86. If he selects high
or low restriction, with valve 82 open, there will be resistance
to contraction of the piston 60 and cylinder 62, reducing any
tendency to jackknife. This selection may be desirable in
particularly slippery conditions. Retraction of the p;ston 60
from cylinder 62 will still be possible due to one way valve 70.
The accumulator 78 is charged with air or another suitable
; 25 gaseous medium which will compress resiliently as the hydraulic
fluid from the cylinder 62 enters the accumulator 7~. When the
force contracting the plston-and-cylinder device i8 removed, i.e.
the driver begins to straighten the vehicle, the compressed air
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or gas will expel the hydraulic fluid from the accumulator 78
and, in so doing, produce a restoring force to assist
straightening of the vehicle.
As mentioned previously, when a trailer is attached which
has not been modified, i.e. does not have a hole in its underside
to receive plunger 56, the trailer pivots relative to support
plate 16. The driver can then prevent rotation of the turntable
26 relative to ths tractor 10 by closing valve 82 completely when
the vehicle is straight. Since the piston-and-cylinder device
will not be able to contract, the turntable 26 will not be
permitted to turn.
It is envisaged that more than one accumulator might be
provided, perhaps coupled each to a different one of a plurality
of restrictors so as to give different degrees of shock
àb80rption a8 well a8 re8trict~0n.
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