This invention concerns a lead on ramp assembly for use
on a vehicle in association with a coupling for attachment of a trailer.
In respect of an articulated lorry, a tractor unit vehicle
is provided with a fifth wheel coupling for attachment of a trailer and a lead on
ramp is commonly provided behind the coupling (when considered in the direction
of travel). Such a lead on ramp typically comprises a pair of spaced apart sloping
beams, which may be of channel section steel, connected by a crosspiece.
The purpose of the lead on ramp is to guide the front of
the trailer upwards to facilitate its coupling, more specifically to facilitate
engagement of a kingpin dependent from a front region of the trailer into a rearwardly
directed slot in the fifth wheel coupling. In the absence of such a ramp, rear mudguards/mud
wings of the tractor unit vehicle may be damaged upon trailer coupling, and even
the chassis itself may be damaged if the trailer is not correctly aligned as coupling
is attempted. However, the presence of the ramp may also cause problems. For example,
an articulation angle of 7 degrees in a vertical direction is usually allowed for
between the tractor unit and the trailer, but when this is near maximum or is exceeded,
e.g. when travelling over steep hills or boarding ferries, the under carriage of
the trailer may contact the ramp and either the ramp or the undercarriage may be
An object of the invention is to avoid the aforesaid problems.
With this object in view, the invention provides a lead
on ramp assembly for use on a vehicle in association with a coupling for attachment
of a trailer, said assembly comprising at least one ramp member having an upper
ramp surface and having means for pivotable mounting relative to a chassis of the
vehicle so as to be movable between a raised operative condition wherein the upper
surface is inclined at a predetermined angle relative to the chassis and a lowered
non-operative condition, drive means for moving said ramp member between its raised
and lowered conditions, sensor means for detecting an arrangement indicative of
attachment of the trailer to the associated coupling and control means operatively
connected to both the drive means and the sensor means whereby the drive means is
caused to move the ramp member to its lowered condition once the sensor means detects
the arrangement indicative of the trailer being attached to the coupling and the
drive means is actuated to move the ramp member to its raised condition once the
sensor means detects that the arrangement is indicative that the trailer is no longer
attached to the coupling.
The drive means may suitably comprise at least one hydraulic
or pneumatic ram. There are various ways in which such a ram or rams may be mounted
and operative to raise and lower the ramp. Additional support means for the ramp
member in its raised condition may be provided, for example in the form of a displaceable
The sensor means may conveniently detect whether the coupling
is closed or open, the arrangement indicating that the coupling is closed being
indicative of attachment of the trailer to the associated coupling, while the arrangement
indicating that the coupling is open being indicative of detachment of the trailer
from the coupling even though the trailer may not, at that stage, have moved away
from the towing vehicle. In this respect, a conventional fifth wheel coupling includes
a release arm which engages a coupling plate in two different positions such that
it projects further out from the coupling plate when the coupling is open compared
to when the coupling is closed, and also at a different angle in these two positions.
The sensor may then comprise a proximity switch mounted on the coupling plate adjacent
the release arm to detect the position of this release arm. However, in other embodiments,
suitable sensor means may be provided adjacent a slot in the fifth wheel coupling
in order to detect more directly either the position of a locking bar which opens
and closes the slot in the coupling, or the presence of the trailer kingpin in a
correct position in the slot for secure coupling of the trailer thereto.
The invention will be described further, by way of example,
with reference to the accompanying drawings, in which:
- Figure 1 is a schematic side view showing how a first embodiment of the ramp
assembly of the invention operates;
- Figure 2 is a similar view showing operation of a second embodiment of the assembly
of the invention;
- Figure 3 is a similar view of a third embodiment of the assembly of the invention;
- Figure 4 is a schematic transverse cross-section of the ramp assembly shown
in figure 3;
- Figure 5 is another schematic side view of a fourth embodiment of the assembly
of the invention; and
- Figure 6 is a view from above of the same fourth embodiment of figure 5.
A first embodiment, as illustrated in figure 1, comprises
two spaced apart, substantially parallel ramp members 10, which are each pivotally
attached by a pivot pin 12 near their rear end to a sloping rear end of a chassis
20 of a towing vehicle (tractor unit). A fifth wheel coupling for attachment of
a trailer is typically mounted onto the chassis 20 in front of the ramp assembly,
but such coupling is not shown here.
Only one of the ramp members 10 is shown in figure 1. These
ramp members 10 are of downwardly open channel section form and may suitably be
connected by a crosspiece (not shown). Respective fluid actuated cylinders 14 (namely
pneumatically or hydraulically operated cylinders) are mounted below each of the
ramp members 10 with extensible rams or pistons 16 engaging into the channel of
the ramp member 10 to raise or lower it. The ramp member 10 is shown in figure 1
in its raised position. The respective cylinders 14 are arranged to operate simultaneously
on the respective ramp members 10 to achieve even upward pressure on the pair of
ramp members 10.
Further fluid actuated cylinders 18, again one for each
ramp member 10, operate to displace respective support blocks 22 into position below
a downward extension 11 at the front of each ramp member 10 once the ramp members
10 have been raised. These cylinders 18 act in synchrony with the cylinders 14 and
act to withdraw the support blocks 22 when the ramp members 10 are to be lowered
again. In a modified version, however, there may be only a single cylinder 18 acting
upon a single support block 22 which is wide enough to fit below and support both
ramp members of the assembly.
The fluid actuated cylinders 14, 18 are operated by a central
control means of the towing vehicle dependent on input from sensor means (not shown)
associated with the fifth wheel coupling to the central control means so that the
ramp members 10 will be raised when the coupling is detected to be open (generally
indicating that the trailer may be about to be connected or moved away) and lowered
when the coupling is detected to be closed (generally indicating that the trailer
has been connected and no longer requires guidance on to the rear of the chassis
A second embodiment, as illustrated in figure 2, also comprises
two spaced apart, substantially parallel ramp members 30, which are each pivotally
attached by a pivot pin 32 near their rear end to a sloping rear end of a chassis
40 of a towing vehicle (tractor unit). Again, only one of the ramp members 30 is
shown in figure 2 and these ramp members 30 may suitably be connected by a crosspiece
(not shown). Each ramp member 30 may be of downwardly open channel section form
for a major part of its length, but with a cross wall connecting between downward
extensions 31 at its forward end to provide a bearing surface for a wedge shaped
block 34 which is moved to and fro by a transversely mounted fluid actuated cylinder
38 to raise and lower the ramp member 30. A piston 36 of the cylinder 38 is extended
to push the block 34 towards the rear of the chassis 40 in order to raise the ramp
Spring means (not shown) are provided to assist the return
of the ramp member 30 to its lowered condition. Thus, a helical spring may be provided
to act between the ramp member 30 at a position near the extension 31 and the chassis
40. Alternatively (or additionally) a suitable torsion spring may act about the
pivot pin 32 to urge the ramp member 30 back to its lowered position.
As with the first embodiment, respective cylinders 38 and
blocks 34 may be provided for each of the ramp members 30 and these should then
be operated simultaneously. However in a modified version a single cylinder 38 may
act on a single block 34 which is wide enough to fit below both of the spaced ramp
members 30. The control of the cylinder or cylinders 38 is as already described
for the first embodiment.
The third embodiment of ramp assembly, as illustrated in
figures 3 and 4, is a modified version of the first embodiment shown in figure 1.
To avoid repetition, only the modified features are mentioned here and the remainder
is the same as already described.
Instead of being in the form of downwardly open channel
sections, the respective ramp members, here denoted by reference numeral 10' for
the single member which is shown, are of T-shaped profile, as is evident from figure
4. The chassis 20', which may be provided as two separate spaced apart side sections,
or may be continuous, extends below the facing, inner sides of the T profiles of
the respective ramp members 10', while the cylinder and piston 14', 16' for raising
each ramp member 10' is mounted below the remote, outer side of the T profile of
each of the ramp members 10'.
The ramp member 10' is also shown in this embodiment as
being angled in longitudinal profile (Figure 3).
The arrangement shown in figures 3 and 4 may provide for
more streamlined fitting of the ramp assembly into the chassis when in its lowered
condition, as depicted in figure 4, and may also allow for easier access to the
cylinders 14' for maintenance and repair etc.
The fourth embodiment of ramp assembly, as illustrated
in figures 5 and 6, is a modified version of any of the preceding embodiments. To
avoid repetition, only the modified features are mentioned here and the remainder
is the same as already described. In this embodiment, the ramp members 50, of which
there are two, but only one shown, as before, and which are raised and lowered by
any of the means previously described, are not pivotally connected directly to the
chassis 60. Instead, they are pivotally connected by hinges 54 to respective additional
brackets 52 which are fixed to the rear end of the chassis 60 and which may themselves
be considered as part of the overall ramp assembly. In a modified version, a single
such bracket may be provided as an elongate strip across the rear of the chassis
The foregoing embodiments are illustrative and not limitative
of the scope of the invention and many other variations in the detail of the configuration,
mounting and operation of the ramp assembly is possible within the scope of the
invention as defined in the claims.