The present invention relates to an automatic hook to be
fixed to the free end of one of the arms of a lifting device of an agricultural
machine, such as a tractor (see. e.g. US-A-3977698).
Hooks for automatically receiving and locking the ball
connector of an agricultural implement have long been used on such lifting devices.
Hooks are known for example comprising a monolithic hook-shaped
body provided with a coupling seat for a ball connector.
Said seat communicates with a rear housing containing a
catch to partially obstruct said coupling seat by the effect of elastic positioning
means, and externally accessible release means by which said catch can be deactivated
against the force of said elastic means.
When the ball connector is inserted into the coupling seat,
the ball connector causes the catch to move rearwards, to then advance by the effect
of the elastic means when the ball connector has been received in said seat.
When in this configuration, if the ball connector is forced
in the direction for its extraction, this is prevented by the catch, which remains
in the locking position unless the release means are operated.
However it can happen, as in fact has been the case, that
that part of the catch facing the ball connector can be accidentally struck such
as to force the catch rearwards and disengage it from the ball connector, with all
the problems that this can involve.
The main object of the present invention is to overcome
the aforesaid problem within the context of a simple and rational construction which
is reliable, robust, of low cost and safe.
In particular, with regard to the safety aspect, the invention
provides an automatic anti-release hook in the sense that it is able to prevent
accidental disengagement of the ball connector when forces are present which tend
to remove it from the ball connector coupling seat.
This object is attained by the characteristic elements
indicated in the main claim.
Preferred embodiments of said elements are defined in the
The constructional characteristics and merits of the invention,
and its method of operation, will be apparent from the ensuing detailed description
given with reference to the figures of the accompanying drawings, in which:
- Figure 1 is a partly sectional side view showing the hook during the insertion
of the ball connector;
- Figure 2 shows the same hook at the end of insertion;
- Figure 3 is a view similar to Figure 2, showing a further operative configuration
of the hook;
- Figure 4 shows the hook in its release configuration;
- Figure 5 is a partial view in the direction V of Figure 4.
Said figures, and in particular Figures 1 to 4, shown a
robust metal body 1 having the characteristic shape of a hook.
Said body 1 presents at its rear a tapered portion 2 intended
to be welded to a lifting device of an agricultural machine, and at its front a
coupling seat 3 shaped as a spherical surface portion.
The seat 3 is provided to receive a usual ball connector
4 of a likewise usual agricultural implement.
As can be seen, the body 1 is traversed by a profiled through
aperture 5 the rear mouth of which opens above the tapered portion 2, whereas its
front mouth faces the upper region of the seat 3.
The aperture 5 houses, in the stated order, a rear profiled
lever or handle 6, and a front catch 7 which is pivoted to the handle 6 by the pin
indicated by 8.
The handle 6 and catch 7 are flat as can be seen from Figure
The catch 7 has a slightly curved lateral profile with
its concavity facing upwards (see Figures 1-4), and in its tip presents a forward
facing groove 9 of cross-section matching the spherical shape of the ball connector
4 (Figure 5).
During the forward and rearward movements of the catch
7, its upper and lower arcuate edges engage, along a substantially linear contact
region, with a transverse pin 10 which passes through the aperture 5, and with an
inclined surface 11 of the aperture 5 itself.
The catch 7 is constantly forced towards the coupling seat
3 by a pair of elastic members 12 and 13, of which the first 12 acts on the catch
7 and the second 13 on the handle 6.
The first elastic member 12 consists of a thrust spring
which is housed within an elongate window 14 situated along the length of the catch
7, and lies between the front end of said window 14 and a transverse pin 15 passing
through the window 14 and aperture 5.
In addition to acting as a counteracting member for the
spring 12, the pin 15 also acts as the limit stop for the forward movement of the
catch 7 (Figure 2).
The pin 15 has a diameter less than the width of the window
14 to enable the catch 7 to undergo its necessary transverse excursions (Figures
1-4). The second elastic member 13 consists of a tension spring which at one end
is coupled to an appendix 33 of the handle 6, and at its other end is coupled to
a transverse pin 16 passing through the aperture 5.
Said appendix 33 is designed to engage (Figures 1 and 4)
the fork-shaped inner end of the catch 7 (Figure 5).
The handle 6 emerges from the rear mouth of the aperture
5 where it presents an eyelet 60 to be connected to a suitable pull cable usually
terminating at the driving seat of the agricultural machine, such as a tractor.
In proximity to said eyelet 60 there is provided, in the
front edge of the handle 6, a first recess 17 acting as a retention pawl, to engage
a forward lying transverse pin 170 passing through the aperture 5.
In the rear edge of the handle 6 there is provided a second
recess 18 acting as an anti-release seat, arranged to engage a transverse pin 180
passing through the aperture 5.
Said first recess 17 faces the coupling seat 3, while said
second recess 18 is positioned in the opposite direction. Finally, in proximity
to said recesses 17 and 18 the handle 6 presents a through hole 19 which can be
aligned with two coaxial holes 190 provided in the sides of the aperture 5, to provide
an engagement seat for a bolt 20 (see Figure 5).
The described hook operates substantially as follows.
Before inserting the ball connector 4, the constituent
elements of the hook lie in the configuration of Figure 2, established by the springs
12 and 13, in which the catch 7 rests against the pins 10 and 15, while the handle
6 lies rearwards with the pin 180 in contact with the upper flank of the recess
18. When the ball connector 4 is inserted into the seat 3, as in Figure 1, it lowers
the catch 7 and pushes it rearwards against the thrust and traction forces of the
springs 12 and 13 respectively, which then return the catch to its previous position
when the ball connector 4 has passed beyond it (Figure 2).
In this position the pin 180 lies at the entry to the recess
18, with the catch 7 preventing the ball connector 4 from leaving its seat 3.
It is prevented from so doing not only when the ball connector
4 is forced upwards, or vice versa the body 1 is forced downwards, but also when
an accidental impact, indicated by an arrow in Figure 3, acts on the tip of the
In such situations the catch 7 withdraws slightly, but
without releasing the ball connector 4, and halts when the pin 180 fully engages
in the recess 18.
To release the ball connector 4 the handle 6 has merely
to be pulled upwards, so causing the catch 7 to withdraw.
Having done this, to deactivate the catch 7 in order to
maintain the hook open, the handle 6 needs merely to be pushed forwards, as indicated
by an arrow in Figure 4, to engage the recess 17 with the pin 170.
Subsequent disengagement of the recess 17 from the pin
170 results automatically in reactivation of the catch 7 by the springs 12 and 13.
The catch 7 can be locked in the active position by inserting the bolt 20 (Figure
5) into its seats 19, 190.