It is known that the agricultural machines are provided with tree-points
connections in order to connect tools thereto, these tools are employed for example
for working country terrain, such connections being constituted by two lower connections
and a third upper connection, whose mutual positions and lay-out are of standard
These connections are modelled so as to therein accommodate conjugate
parts with which the agricultural tools are provided.
These connections must keep the tool firmly secured in operating
condition, must be disengaged from the conjugate parts of the tool when their disengagement
is required, but they must have no opportunity to accidentally disengage during
the working operations.
Since at least 1989, it is known a hook for third upper point of
such connections, comprising a hook-shaped body having a hollow portion wherein
a first end of a shutter is axially movable that can be engaged, when the shutter
lies in its closing position, against the conjugate surface of a tool so as to
block it in its working operative position.
The shutter is furthermore provided with a second end, to which a
lever, actuatable by the operator, is hinged through a hinge pin; the lever is
also hinged to the hook-shaped body in order to move the shutter from the closing
position to an opening position, wherein it is pulled out of the hollow of the
hook-shaped body, releasing the conjugate portion of the tool. The lever is provided
with an L-shaped slit having a first branch disposed substantially parallel to
the axis of the shutter when it lies in the closing position and a second branch,
substantially perpendicular to the first branch.
The lay-out is such that, when the shutter lies in closing position,
the hinge pin occupies the first branch of the L-shaped slit.
Therefore, possible loads that were accidentally transmitted to the
shutter by the conjugate portion of the tool causing it to recede from the hollow
and release the tool, are prevented by interference of the pin with the first branch
of the L-shaped slit.
According to the Italian utility model patent n. 228875, the first
branch of the L-shaped slit is provided with a small retaining groove in order
to block the hinge pin in the closing position of the shutter.
In the above illustrated hook, in order to prevent the conjugate
portion of the tool from overloading the shutter for causing it to further fall
into the hollow, producing an anomalous stressing of a flat spring disposed between
the lever and the hook-shaped body and acting so as to hold the lever close to
the hook-shaped body, a transversal pin is provided secured to the shutter so as
to release said stresses on the hook-shaped body.
The application of this transversal pin implies a remarkable increase
of costs and assembling problems that produce waste of time.
Furthermore, it is required a quite meticulous manufacturing of the
portions of the hook-shaped body that interact with the above-mentioned pin.
A purpose of the invention is to improve the existing connections,
and more in particular to make more cost-effective these connections, with reference
either to the manufacturing and to the assembly.
According to the invention, hook means is provided, comprising a
hook-shaped body provided with a hollow suitable to be coupled with a conjugate
portion of an agricultural tool, a shutter slidably inserted into said hook-shaped
body so as to partially occupy said hollow with a first end portion thereof and
having a second end portion coupled to an actuating lever, said actuating lever
being held adjacent to said hook-shaped body by elastic means, stopping means
suitable to cooperate with said lever when it lies close to said hook-shaped body,
characterized in that, said stopping means is associated to said hook-shaped body.
In this way, the manufacturing of the connection results simplified,
because for the manufacturing of the stopping means there is no need for machining
to be performed onto the shutter.
The invention will be better understood and carried out with reference
to the accompanying drawings, wherein:
- Figure 1 is a side view of a hook for third upper point of an agricultural
tractor, in opening position;
- Figure 2 is a view like Figure 1, but in closing position.
As shown in the Figures 1 and 2, a hook-shaped body 1 shows a hollow
2 suitable to shapingly receive a pivot 3 of an agricultural tool, not shown.
A hinge pin 4 is provided on the external portion of the body 1 to
which a lever 5 is coupled in an oscillating way, moving between a closing position
close to the body 1 and an opening position wherein the lever 5 lies remarkably
separated from the body 1. A slit 6 is obtained into the body of the lever 5 at
its coupling region with the pin 4. The slit 6 is modelled as an L shape and shows
a first branch 7, lying - in the closing position of the lever 5 - substantially
parallel to a shutter stem 9 and a second branch 8 perpendicular to the first
branch 7 and suitable to allow the rotation of the lever 5 when this must be brought
to the opening position.
The stem 9 shows a first end portion 10 suitable to partially occupy
the hollow 2 in order to engage the pivot 3 and a second end portion pivotally
coupled to the lever 5 through a moving pin 12.
The stem 9 is slidable into a bore 13 passing through the body 1
and is provided with a seat 14 for a recovery helical spring 15.
Onto the body 1 a transversal peg 16 is provided suitable to interfere
with cooperating surfaces 17 of the lever 5 in order to prevent the lever 5 from
approaching the body 1 beyond a pre-established limit, when the stem 9 is pressed
along the direction of the arrow F. In this way, also the recovery spring 18 of
the lever 5 is not stressed when forces directed along the direction shown by the
arrow F are released onto the shutter.
The peg 16 is advantageously parallel to the pin 4, so as, while
the manufacturing necessary for the positioning of the pin 4 is performed, also
the manufacturing relative to the peg 16 can be carried out.
Furthermore, no type of machine tool working is required, either
for the peg 16 or for the cooperating surfaces 17.
Obviously, according to a version not shown, instead of the peg 16,
a conformation of regions of the body 1 can be provided corresponding to the conformation
of the cooperating surfaces 17, in order to receive cooperating abutting surfaces.
In this case it is furthermore necessary a tool machining of the body 1, that can
take place when the body 1 is already prepared for the machining relative to the