Note: Descriptions are shown in the official language in which they were submitted.
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COUPLING MECHANISM
FIELD OF THE INVENTION '-
This invention relates to a coupling mechanism.
The principal use for the invention is as a hitching
device for interconnecting a towing and a towed vehicle, and
the example of the invention illustrated and described in
detail below is such a hitching device. Nevertheless, the
invention in its broad aspect can be employed as a general
coupling mechanism for other purposes.
PRIOR ART
Coupling mechanisms are known, both for conventional
towing and as fifth wheel devices, in which a pair of j aws are
movable to a closed position in which they close around a pin,
the jaws being locked in this closed position to maintain a
- 15 connected coupling until they are released in some suitable
manner, usually manually.
Such hitching couplers are disclosed, for example, in
P.J. Culhane U.S. patent 1,233,849 issued July 17, 1917; R.D.
Tracey U.S. patent 2,676,034 issued April 20, 1954; and G.C.
Monckmeier U.S. patent 2,798,741 issued July 9, 1957; and as
fifth wheel couplers in W.D. Walther et al U.S. patent
Z 3,787,076 issued January 22, 197~ (corresponding Canadian
patent 956,339 issued October 15, 1974); T.B. Dalton Canadian
patent 650,880 issued October 23, 1962; and P.M. Davies
Canadian patent 1,042,475 issued November 14, 1978.
,.! SUMMARY OF THE INVENTION
The object of the invention is to provide improvements in
such a mechanism, and in particular to provide a coupling
mechanism that is more convenient to use.
In particular, it is an object of the invention to
provide a coupling mechanism that will be both more reliable
in use and more compact in the front-to-rear direction than
former constructions, and that will be capable of being
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readily mounted in the limited space typically available at
the rear of a towing vehicle.
To this end, the invention consist of a coupling
mechanism comprising a pair of parallel plates interconnected
in a spaced relationship and together defining an opening for
receiving a pin oriented perpendicular to the plates. A pair
of jaws is pivotally mounted between the plates to be movable
between a closed position coupling with the pin and an open
position releasing the pin. The jaws have respective faces
that in the closed position define a space. A locking member
is slidably mounted for movement through one of the plates
between a locking position extending through the space between
the jaw faces and into engagement with the other plate to
retain the jaws in the closed position, and a withdrawn
position permitting movement of the jaws to the open position
to allow withdrawal movement of the pin from the mechanism. A
third plate is secured parallel to and spaced below the lower
one of the first and second plates, said lower and third
plates defining a space for receiving a horizontally oriented
load transmitting plate attached to the pin for transferring a
vertical force to the coupling mechanism. In the preferred
embodiment, when the jaws are in the closed position, the jaw
faces engage surfaces on opposite sides of the locking member
so that a force urging the jaws to their open position, i.e. 25 urging the jaw faces together, is resisted by compression of
the locking member.
Preferably, the locking member will be spring urged
towards its locking position, and the jaws will be spring
urged towards their open position, with the jaw faces that
define the space in the closed position limiting the opening
movement of the jaws.
As an additional safety consideration, the coupling will
also preferably include a pair of additional locking members,
each for extending through both of the plates and a respective
jaw, for retaining the jaws in the closed position.
The invention is also directed to a combination of the
coupling device defined above and a pin assembly to be mounted
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on apparatus to be coupled to the coupling device, e.g. a
conveyance to be towed, such pin assembly preferably taking
the form of a pair of spaced plates between which the pin that
is engaged by the jaws extends.
Also in the preferred embodiment, the plate assembly is
pivotally mounted on a base that is adapted for securing to a
towing vehicle, such pivotal movement taking place about a
horizontal, transverse axis.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is an exploded perspective view of two parts of
a hitching device according to one embodiment of the
invention, shown in its uncoupled condition;
Figure 2 is a plan view of Figure 1;
Figure 3 is a similar plan view with the parts in the
coupled condition; and
Figure 4 is a partially sectioned, side view, as seen
from below Figure 3.
DETAILED DESCRIPTION OF THE EMBODINENTS
The embodiment of the invention illustrated in Figures 1-
4 is a coupling device consisting of a hitch mechanism H
adapted to be secured to a towing vehicle and to receive and
; become coupled to a pin assembly P that will be attached to a
conveyance to be towed.
; The hitch mechanism H includes a plate assembly
consisting primarily of a parallel, spaced-apart pair of
horizontal plates 4 and 6, having frontal, divergent openings
4a, 6a, respectively, and between which a pair of movable jaws
5 is located. Each jaw 5 is pivotable about a vertical pin 2
extending between the plates 4 and 6, and the jaws are movable
between an open position shown in Figures 1 and 2 and a closed
position seen in Figures 3 and 4. Each jaw 5 has a semi-
circular cut-out portion 5a that, in the closed position,
embraces a pin 11 of the pin assembly P to couple the two
assemblies together, the pin 11 having been guided into the
hitch mechanism H by the openings 4a, 6a of the plates 4, 6.
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Each jaw 5 has an inclined face 5b at its rear. For
convenience, the left hand end of the hitch mechanism H as
seen in the drawings will be considered as its rear, although,
when mounted on a towing vehicle, this end will be nearer the
front of the vehicle. When the jaws 5 are open these two
faces 5b abut each other to limit the open position (Fig. 2),
the jaws being urged towards this position by a coiled tension
spring 14, each end of which is connected to a respective jaw
at 14a.
However, when the pin 11 is pushed to the left into the
jaws 5, as seen in Figure 3, it exerts a force on each jaw to
turn it about its pivot pin 2 against the tension of the
spring 14. This movement separates the jaw faces 5b,
providing a space between these faces, into which a vertical
locking member 1 can slide downwardly under the action of a
spring la. The locking member 1 is mounted in a framework lb
secured to the upper plate 4, so as to be vertically slidable
through a hole 4b in the upper plate 4 and the space between
the rear jaw faces 5b, into a corresponding hole 6b in the
lower plate 6 (see Fig. 4). The spring la retains the locking
member 1 in this downward (locking) position until it is
pulled upwards manually to its withdrawn position using a
finger ring lc, whereupon the spring 14 will act to open the
jaws 5 and release the pin 11, assuming that the pin is no
; 25 longer exerting an inward force on the jaws.
Further safety for retaining the jaws in their closed
position and hence the device in its coupled condition can be
provided in ~he form of safety locking pins 3 that are
inserted manually through aligned vertical holes in the upper
plate 4, jaws 5 and lower plate 6.
In the p,n assembly P the pin 11 extends vertically
between a lower plate 10 and an upper member 12, these parts
being secured to a shaft member 13 whereby the assembly P can
be secured to a conveyance to be towed (not shown).
The upper plate 4 extends into vertical side plates 15
(Figure 1) that serve to secure the two plates 4 and 6
together and also to secure beneath them and spaced from the
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ower plate 6 a further horizontal plate 7. The space between
the plates 6 and 7 serves to receive the plate 10 of the
assembly P, the front edges 6c and 7c of these plates being
inclined to the horizontal to help guide the plate 10 into
such space, as best seen in Fig. 4.
The mechanism H is mounted on a base 9 by means of a
horizontal, laterally extending, swivel mechanism in the form
of a pin 8. The base 9 will be secured to a towing vehicle
(not shown).
It is an important feature of the present invention that
the primary locking member 1 slides vertically when entering
the space between the jaw faces. This arrangement, in
contrast to the use of a horizontally sliding member, as
employed in many prior devices, has the advantage that the
15 mechanism is more compact in the front-to-rear direction. In
practice there is often very limited space between the rear of
the hitch mechanism H and the framework of the towing vehicle,
e.g. when mounted on the drawbar of a farm tractor or on the
back framework of a tandem axle truck. To accommodate a
20 horizontal, rear entry pin, as proposed for example in the
patents to Tracey, Walther et al, Dalton and Davies mentioned
above would in many cases require a physical alteration to the
back portion of the towing vehicle on which the hitch
mechanism is to be mounted. Apart from being expensive, such
25 alterations often cannot be made without adversely affecting
the performance of the towing vehicle. In the Monckmeier
patent, although the latch member 52 enters the space between
the jaws by means of a vertical movement, such movement is a
pivotal one that takes place about a shaft 54 located to the
30 rear of the latch member 52. Hence again the locking
mechanism extends significantly to the rear beyond the rear
edges of the jaws, a space requirement that the present
invention avoids by employing a vertically slidable locking
member to enter the space between the jaws.
As a result, a very practical advantage of the vertical
- entry, sliding member 1 of the present invention is that the
back edge of the hitch mechanis H can be mounted flush to any
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.nounting framework, while still enabling the movable locking
jaw concept to be used.
In addition, the present invention provides a
construction in which the locking member 1 not only enters the
space between the jaws 5, but in doing so passes through a
hole in both the plate 4 above the jaws and the plate 6 below
the jaws. This support of the member 1 both above and below
its central portion that is engaged by the jaw faces 5b avoids
any risk of the free end of the pin 1 being pushed aside or
1~ bent by the jaws.
It is also significant that when the jaws are in the
closed position their rear surfaces 5b engage surfaces on
opposite sides of the locking member 1. As a result, a force
urging the jaws to their open position is resisted by
compression of the locking member 1. This is an important
distinction over the mechanism disclosed in the Culhane patent
referred to above where rear faces of a pair of jaws are
engaged by a member 4 the releasing movement of which can be
restrained by a pin 20. It is this pin 20 that resists
opening of the jaws, and this pin is stressed in shear across
its cross-sections located in the planes between the member 4
and the fixed plates 13 and 14. As is well known, in contrast
to a member that is subjected to shear forces across its
width, a similar member that is subjected to a transverse
compression force is much less likely to fail and can
withstand much large forces before yielding. Alternatively it
can be made with a smaller transverse dimension (diameter,
when the locking member is a cylindrical pin) than would be
required to resist its shearing.
A further advantage of the present invention over the
Culhane mechanism resides in its simplicity, and, in
particular, the avoidance of any front-to-rear sliding action
such as is represented by Culhane's member 4. The member 4 is
fixed, being a drawbar that is connected to a towing vehicle,
while the remainder of his coupling mechanism slides over the
member 4. This arrangement means that the Culhane mechanism
oannot be rountod flush again~t a plate such as a bumper of a
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pickup truck, the back of a gravel truck to pull a trailer
unit, on a modern agricultural drawbar, or on a modern highway
transport unit. In many cases, a flush mounting is mandatory
and a mechanism like Culhane's requiring room to slide would
be unusable. Keeping the overall length to a minimum is an
important cvnsideration in hitch devices and a major advantage
of the present construction.
A still further advantage of the construction illustrated
in the drawings resides in the provision of the secondary
safety pins 3 which also pass through the plate 4 above the
jaws 5 and into the plate ~ beneath them.
Another significant feature of the device described
herein is the provision of the third and lowermost plate 7 as
a vertical load bearing part of the hitch mechanism H, since
lS the plate 7 receives a downward vertical force from the plate
10 of the pin assembly P. In prior proposals the vertical
load bearing capacity of the hitch mechanism has been provided
above the locking jaws, which is a reason why the locking pins
have usually been arranged to enter the jaws horizontally. In
the present arrangement, on the other hand, since the load
bearing capacity of the plate assembly (plate 7) is below the
jaws 5, the primary locking member 1 (and indeed also the
secondary locking pins 3) can enter from above and hence be
readily accessible, at the same time achieving the horizontal
space saving advantages already explained. The load bearing
plate 7 of the hitch mechanism H thus cooperates with the load
transmitting plate 10 of the pin assembly P in a novel manner.
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,UPPLEMENTARY DISCLOSURE
Figure 5 is a view similar to Figure 1 of a further and
preferred embodiment. In Figure 5 the base 9 is replaced by a
base 9' in a modified hitch mechanism H'. The base g' extends
around the rear of the plates 4, 6 and the jaws 5 to support a
swivel mechanism in the form of pins 8' that project laterally
inwardly to each side plate 15. The horizontal transverse
axis defined by the swivel pins 8' is aligned with the centers
of the cut-out portions 5a of the jaws 5 in both the
horizontal front-to-rear direction and the vertical direction,
so as to be aligned with the vertical axis of the pin 11
approximately midway of its height when the jaws are closed
and the pin 11 is locked in the towing position illustrated
for the first embodiment in Figure 3 and which will be
essentially the same for the second embodiment of Figure 5.
This alignment of the swivel axis with the pin 11 minimizes
wear in use. The other parts of the hitch mechanism H' are
;~ basically the same as the mechanism H, and the assembly P' is
also basically the same as the assembly P except that in the
assembly P' the parts 10, 11, 12 are pivotally secured to the
shaft member 13 so as to be freely rotatable about a
horizontal, front-to-rear axis. Each side plate 15 is
attached to the lowermost plate 7, as in Figure 1, except that
the attachment is further to the rear and hence not visible in
Figure 5, in order to permit a large arc of movement of the
' plates 4, 6 about the pin 8'.
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