Note: Descriptions are shown in the official language in which they were submitted.
The in~ntion relates to a coupling rnechanism for
agricultural trailer units. More specifically, the invention
rela-tes to such a mechanism comprising, at i-ts front end, a tow-
bar fitted with a coupling element, the said towbar beiny adapted
to move longitudinally and transversely wlthin a range defined
by a guiding device, and to be locked in a central position.
A coupling mechanism of -this kind is already known from
German Utility Model 73 26 989. Thi~ mec~an.ism has an elonyate~,
trapezoidal frame arranged to pivot in a vertical plane on the
relevant trailer uni-t, and it is tranversed longitudinally by the
towbar. In the simplest form of the said coupling mechanism, the
guiding device consists of two guide paths arranged within the
frame and a guide part mounted pivotably at the front end of
the frame and equipped with guide rollers, the towbar being
adapted to be locked in its central position b~ means of a lock-
ing mechanism located at the rear end of the frame.
The towing device in accordance with the invention, is
intended to simplify considerably the process of coupling a
trailer unit to a tractor, it being sufficient to move the
: tractor, approximately in the direction of the coupling mechanism,
: 20 towards the trailer unit to be coupled, until the tractor coupling
is located within the range o~ ~ovement of the coupling element
of the trailer coupling mechanism. However, this is.quite easy
to ùo, even if neither the tractor coupling nor the coupling
nor the coupling mechanism on the trailer unit can be seen from
;~ the driverls seat of the tractor.
ven in its simplest form, the known coupling mechanism
has the considerable ùlsadvantage of belng highly complex and
expensive. Another disadvantage is that the elongated frame of
the coupling mechanism prevents the trailer unit from being
~30 locateù as closely as possible to the tractor, which is desirable
in the case of certain ~trailer units such as drilling machines,
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for example, or, if -this d.isadvantage is overcome by usiny
a towbar which, in its central locked position, projects only
slightly in a forward direction from the frame, then i-t restricts
the turning radius of the train to an extent such that very wide
turning areas mus-t be lef-t free at: each end of the field wher
the sald train is in opera-tion.
Now it is the purpose of the invention -to achieve, by
subs-tantially simpler means, the ability of known mechanisrn
to facilitate -the coupling of a trailer unit to a -tractor or to
a preceding trailer unit.
According to the invention, -this purpose is achieved
in that the guiding device consists of a guide part rigidly
attached to the towbar and spaced laterally therefrom, and of a
carrier, the outer end of which is mounted pivotably upon the
free end of the said guide part, and which, when the towbar is in
the locked position, projects therebeyond to the other side, where
it is arranged pivotably upon a frame par-t forming a part of the
trailer unit.
This arrangement makes it possible to keep the frame
of the coupling mechanism very short, as seen in the direc-tion
of travel, or the said frame may consist of a single carrier
arranged to pivot in a vertical plane upon the frame of the
trailer unit to be coupled. Furthermore, in the case of single-
axle trailer units, no separate frame is required for the coup-
ling mechanism. Instead, the frame part upon which the carrier
of the guiding device is arranged to pivot, may be included in
the frame of the unit. The turning radius of the tractor and
trailer unit is then determined merely by the lenyth of the tow-
bar, since the length of the frame of the known coupling mechanism
is thus eliminated.
According to one preferred example of embodiment of the
invention, a locking part is -fitted to the towbar and a locking
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lever is mounted pivotably upon -the frame ~ar-t and has a pro-
jection adapted to move over sald loc~incJ part. The said locking
lever is connected to a resllient elemen-t ac-tiny in the
direction of the said locking part, the range over which the
said locking lever pivots being restricted, in the forwardly
directed position and against the -tension of said resilient
element, by a stop. The front of the said projection has a
surface sloping obliquely Eorwards. This is a simple way of
providing fully automatic locking of the towbar, so that the
driver needs to leave his seat only once, -to carry cut the
actual coupllng, i.e. to connect -the -tractor coupling element to
the coupling mechanism.
If the coupling element on the towbar, when the latter
is in its locked position, is loca-ted upon the centreline run-
niny, when the train is moving in a straigh-t line, forwardly
between the two bearings on the carrier, then the -towbar is
safely guided, after the coupling operation, in its locked
position, when the tractor is moved back. This is improved
still further by the provision of a stop which limits the extent
to which the carrier can pivot to an angle of 60 in relation to
its initial locked position. This is to ensure that even a
force produced by moving the tractor back, and acting obliquely in
an outward direction upon the said carrier, cannot pivot the
latter into an outward position in which the towbar would not be
locked. If the tractor and a unit already coupled thereto, is
moved back in an oblique direction towards a trailer unit to be
coupled, then, after the coupling operation, the tractor need
be moved only a short distance forwards un-til the carrier of
the coupling mechanism bears against the stop. Since in this
position, both the towbar coupling element and the guide-ar-t
bearing must be located in front of the central area of the
coupling mechanlsm, the towbar will be moved safely into its
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loc~sed posi'ion when -the backward movement takes place.
In order to prevent automatic release of the locking
lever from the locking part during travel at high speeds over
uneven ground, provision is made, according to ~he invention, ~or
the locking lever to be locked additionally, by means of a pin,
to the carrier and the towbar, when the latter is in its locked
position. In this case, a particularly stable and reliable
design is obtained, in that the locking lever is located above
both the carrier and the towbar and ~is connected to, and secured
against rotation in relation to, a second locking lever of the
same kind and in the same position below -the carrier and the tow-
bar, with the locking part projecting through the towbar.
If a handle projecting freely in an upward direction
is secured to locking lever located above the carrier and the
towbar, this provides the additional advantage of easy and con-
venient actuation of the locking lever, or levers, during un-
coupling of the trailer unit.
In accordance with a specific embodiment of-the
invention, a coupling mechanism for agricultural trailer-
units comprises: a coupling element movable within aspecific range and mounted at one end of a towbar; said
towbar being adapted to be locked in a towing position by
means of a spring loaded lockingimeans, said towbar bein~
connected, at the other end thereof, to one end o~ a guide
part, the other end of said guide part being pivotably
connected to one end of a carrier, the one end of said
carrier projecting from said towbar towards said guide
part when the mechanism is loc~ed in said towing position,
characterized in that the one end of the towbar comprises
the forwardly projecting end thereof; and in that the said
towbar is secured rigidly to the guide part, and the locking
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means is in the form of a pivotably arranged locki.ng lever
adapted to be locked by means of a locking part, the said
locking lever comprising, for locking purposes, a projec-
tion and a surface running obliquely outwards against the
action of a resilient element, and the pivoting range of
said locking lever being limited, by a lever stop, to a
position in which the said surface of the projection comes
into contact with the locking part when the coupling element
is moved into the locked towiny position.
The invent.ion is expla.ined in greater detail
hereinafter in conjunction with the drawing attached hereto,
wherein:
FIGURE 1 is a plan view of the coupling mechanism
according to the invention in the locked
position:
FIGURE 2 is a section along the line A-B through
the same coupling mechanism, and
FIGURE 3 is a plan view of the same coupling
mechanism with the lock released.
The coupling mechanism comprises a towbar 1
equipped at its front end w~th a coupling element 2 and
with its rear end connected to a guiding device 3. The
latter consists of a forked guide part 4 welded to tow-
bar 1 and spaced laterally therefrom, and of a carrier 5,
one end of which is arranged to pivo-t in a bearing 6 at
the free end of guide part 4. In the locked position
shown in Fig. 1, carrier 5 extends to the other side
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beyond towbar 1, -the other encl of the said carrier being also
pivotable in a bearing 7 located in a frame part 8, the latter
being connected in any known manner, not shown, to the trailer
unit to be coupled up. In this case, coupling element 2 is
located exactly upon centreline 10 which passes, when the train
is running in a straight line, in a forward direction between
bearings 6 and 7 of carrier 5.
Furthermore a locking par-t 11 is secured to towbar 1,
the said part projecting from the towbar on both sides and being
located, when the mechanism is in the retrac-ted posi-tion, close
to carrier 5, so that the said towbar cannot be pivoted rear-
wardly beyond carrier 5. Mounted ro-tatably in frame paxt 8,
behind towbar 1 is a pin 12 which projects on both sides from
frame par-t 8, a forwardly projecting locking lever 13 being
secured, on each side of the frame, to the projecting ends of
said pin. The front end of each of the said locking levers has
projection 14 adapted to pivot over the outwardly projecting
ends of locking part 11. In order to prevent locking levers 13
: from pivoting inwardly towards bearing 7 of carrier 5, they
are connected together, above frame part 8 by a s-top 15. A
resilient element 16 is secured to the each projecting end of
the stop, the other ends of these elements being secured to
frame part 8 and thus applying to locking levers 13 a force
causing them to bear against locking part 11 and stop 15.
In order to achieve, during the locking operation,
~automatic return of locking lever 13 against the force of res-
ilient element 6, the front end of each locking lever 13 is
provided with a surface 17 which slopes obliquely in a forward
direction. Also~secured to upper locking lever 13 is a handle
18 projec-ting freely upwards. For the purpose of securing
: towbar 1 additionally in its locked position, holes 19 are
located ln the lower~part of the said towba~, halfway along
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carrier 5, and in lockiny levers 13. When towbar :L is in its
locked position, locking pin 20 is inserted into holes 19.
When this lockin~ pin is not in use, it may be inserted into
sleeve 21 welded to frame part 8. Finally, a stop 22 is pro-
vided in front of bearing 7 in carrier 5. As shown in Fig. 3,
this stop restricts the range over which carrier 5 may pivot
from its locked position to an angle~ of 60.
The procedure for coupling a trailer unit to a tractor
is as follows:
The tractor is first moved towards the coupling
mechanism until the trailer coupling thereof is located wi-thin
the range of movement 23 of coupling element 2, indicated in do-tted
lines in Fig. 3. Since -this covers a relatively large area, it
is quite possible for the tractor driver to accomplish this
maneuvre, even when the closeness of the -tractor and the trailer
unite prevents him from seeing -the coupling member from his
seat on the tractor.
Locking pin 20 is then removed from holes 19, upper
locking lever 13 is pivoted rearwardly until its projection 1~,
and therefore also projection 1~ of the lower locking lever, are
released from locking part 11, and towbar 1 is pulled forward
un-til coupling element 2 can be coupled to the tr~iler coupling
on the tractor. Since the tractor wlll relatively
located centrally and straight ahead oE the coupli.ng mechanism,
the tractor, with the trailer unit, should always be driven a
short distance straight ahead, so that the coupling mechanism may
assume the extended configuration shown in Fig. 2. This brinys
carrier 5 up against stop 22, while bearing 6 and coupling
elemcnt 2 are located exactly upon the centre line.
The tractor is then moved back, causing towbar 1 and
guide part ~ to pivot in the direction of arrow 2~, and carrier
5 in the direction arrow 25. Towards the end of these movements,
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lockinc~ part 11 lmpinges upon oblique surfaces 17 o:E locklng
levers 13 which are therefore forcecl back ~gainst the action
of resilient elements 16, until projections 1~ are in -front
of the said locking part and are pulled into the locked position,
shown in Fig. 1, by resilient elements 16. Lockiny pin 20
may now be reinserted into holes 19 which are now aligned with
each other.
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