Apparatus for the parking lock of an agricultural vehicle

An apparatus for the parking lock of a vehicle, in particular, of an agricultural tractor. The apparatus comprises a parking lever mechanically linked to a braking lever by a cinematic chain. The braking lever comprises a tooth apt to engage at least a braking element vehicle. The braking lever is provided with a yielding device placed in correspondence to its own hinge. The yielding device is able to ease the engagement of the tooth with a gap comprised between two teeth of a driveline gear in order to guarantee a reliable parking lock of the vehicle.

The present invention concerns an apparatus for the parking lock of a vehicle, in particular of an agricultural tractor. In particular, the present invention is advantageously, but not exclusively, employed in the field of agricultural tractors, to which the following description will explicitly refer without losing its general meaning.

As already known, in the field of agricultural tractors apparatuses for parking lock are used which comprise a parking lever mechanically linked to a working lever by means of a cinematic chain. Furthermore, the working lever comprises a tooth which engages a braking element of the vehicle, said element being formed, in most cases, by a driveline gear fitting on the shaft of the conic pinion which brings motion to the differential box.

One of the disadvantages remarked in the use of said apparatuses is represented by the fact that, when the vehicle is loaded, if the tooth of the working lever does not exactly engage one of the gaps placed between two teeth of the braking driveline gear, a sudden turning of said braking driveline gear could occur, which on its turn could cause the breaking of at least one of the two teeth, thus removing the parking lock.

Therefore, if the tractor with trailer is parked on a slope, the sudden breaking of one of the two teeth (or even both of them) evidently involves the brake release.

It is clear that all the aforesaid can have disastrous consequences when the vehicle, no longer locked and on a slope, starts moving downwards out of the driver's control.

Therefore, the aim of the present invention is creating an apparatus of the parking lock of a vehicle which is free from the aforesaid disadvantages and which can at the same time be easily and economically produced.

DETAILED DESCRIPTION OF THE INVENTION

InFIG. 1the reference number10globally indicates an apparatus for a parking lock which in particular can be suitably applied to an agricultural tractor.

The apparatus10, as it will be better understood hereinafter, acts on a driveline gear11fitted on a shaft12which, on its free end, also supports a conic pinion (not shown) bringing motion to the differential housing (not shown).

Moreover, the apparatus10comprises a parking lever13for the manual insertion of the locking function of the driveline gear11, and therefore of the whole vehicle. The parking lever13is mechanically linked to a braking lever which, as it will be seen, directly acts on the driveline gear11by means of a cinematic chain (CC) whose components will be described hereinafter.

The parking lever13is hinged to the vehicle frame by means of a hinge (HG1) and is provided with a blocking device (BD) of the position of said parking lever13once it has been pushed downwards by the driver of the vehicle.

As shown in more detail inFIG. 2, the device (BD) comprises a groove (SCN) which, on its turn, is provided with an upper dead point (PMS), wherein the parking lever13is placed when the vehicle is in motion, and with a lower dead point (PMI) wherein said parking lever13is housed if the driver inserts the locking function of the vehicle. In the groove (SNC) a path (PRC) is defined between the upper dead point (PMS) and the lower dead point (PMI) which is followed by the parking lever13when the driver wants to select the parking brake. It is clear that the parking lever13follows the path (PRC) in the opposite direction if the parking brake is removed by the driver. In this case the driver must push downwards the parking lever13so that it is freed from the lower dead point (PMI) and then said parking lever13is raised upwards till the upper dead point (PMS).

The cinematic chain (CC) comprises a bar15hinged to the parking lever13by means of a hinge (HG2).

Two plates16,17are fixed to the bar15. Furthermore, the bar15crosses a through hole18made on a cylinder19, also provided with a central room20. As shown inFIG. 1, the through hole18connects the central room20to the outside.

The plate16is placed outside the central room20, whereas the plate17is housed in the central room20and leads the cylinder19. Moreover, a helical spring21is placed between the plate16and a side19A of cylinder19, said spring being compressed when the parking lever13is pushed downwards by the operator according to a direction given by an arrow (F1) (FIG. 1). Obviously, the compression of the helical spring21causes a downward movement of the cylinder19.

A connecting rod22is hinged to the cylinder19by means of a hinge (HG3). A fork23is fixed to the connecting rod22.

Both the connecting rod22and the fork23, integral to each other, are hinged to the frame by means of a hinge (HG4).

As shown inFIG. 1, a first latch24is placed between the prongs23A of the fork23which, on its turn, is integral to a first end25A of an intermediate lever25apt to horizontally slide in a guide26.

A second latch27is placed in correspondence to a second end25B of the intermediate lever25, said latch27being housed in use in the gap between the prongs28A placed on the first end28B of a transmission element28.

A second end28C of the transmission element28is provided with a suitably shaped cam29. Furthermore, the transmission element28is hinged to the frame by means of a hinge (HG5).

The cam29relies on an upper surface14A of the working lever14which is hinged to the frame by means of a hinge (HG6).

A tooth30is placed on a lower surface14B of the braking lever14and in correspondence to its free end, said tooth being able to engage, in use, a gap31comprised between two teeth32,33of the driveline gear11(see hereinafter).

A correct insertion of the tooth30in the gap31allows to lock the driveline gear11, the shaft12and therefore the whole vehicle.

In actual use, if the driver pushes downwards the parking lever13according to the arrow (F1), this causes a lowering of the bar15and of the cylinder19following directions respectively indicated by an arrow (F2) and by an arrow (F3). The bar15glides in the through hole18, whereas the cylinder19glides on the plate17in the room20.

The turning of the connecting rod22and of the fork23, integral to each other, around the hinge (HG4) (following the direction given by an arrow (F4)) causes a translation of the latch24, and therefore of the intermediate lever25, following the direction indicated by an arrow (F5).

On its turn, the latch27, engaged in the gap between the two prongs28A, causes a turning (following a direction given by an arrow (F6)) of the transmission element28around the hinge (HG5).

In this way it is obtained a rolling of cam29on the upper surface14A of the braking lever14. Therefore, the braking lever14lowers itself following a direction indicated by an arrow (F7).

In an ideal working situation of the apparatus10, said lowering of the working lever14and of the tooth30involves, as previously said, the insertion of said tooth in the gap comprised between two teeth32,33of the driveline gear11(FIG. 3) and the steady braking of this latter. As previously stated, a steady braking of the driveline gear11involves a steady braking of the shaft12of the differential conic pinion and therefore of the whole vehicle.

However, during the parking step, the ideal situation shown inFIG. 3does not always occur.

In fact, it is often given one of the two situations shown inFIGS. 4 and 5.

In the situation shown inFIG. 4, after the braking, the tooth30of the braking lever14is placed exactly above the ridge of the tooth33of the driveline gear11.

In this case the driver has lowered the parking lever13from the upper dead point (PMS) to the lower dead point (PMI) for braking the vehicle, without causing particular drawbacks. Therefore, since the parking lever13is now in the lower dead point (PMI), the driver assumes that the vehicle is correctly locked.

This is not correct, since the tooth30rests on the ridge of the tooth33and does not block the system. However, as soon as the vehicle, for instance a tractor with a trailer, is loaded, a small turning of the driveline gear11can occur due to the impact of the load in the trailer, which causes the tooth30to reach the gap31, thus recreating the condition shown inFIG. 3. In this way an accidental correct parking lock of the vehicle is obtained.

A more critical situation is certainly the one shown inFIG. 5, wherein an edge (SP) of the tooth30is blocked on an external portion of a side (FNC) of the tooth33.

In this case, if the trailer is loaded, the sudden impact of the load in the trailer will cause a sudden turning of the driveline gear11which can cause the breaking of at least one of the two teeth30,33, thus disengaging the parking lock. Therefore, if the tractor with a trailer is parked on a slope, the sudden breaking of one of the two teeth30,33(or even of both of them) evidently involves the release of the lock, thus no longer blocking the driveline gear11, the shaft12and therefore the whole vehicle.

It is clear that this can have disastrous consequences when the vehicle, non longer locked and on a slope, starts moving out of the driver's control.

Therefore, in order to solve this problem, it has been thought to apply an innovative yielding device40to the breaking lever14in correspondence to its own hinge (HG6).

In its simplest embodiment, said yielding device40comprises a hole41wherein the hinge (HG6) is inserted together with two helical springs42,43.

The helical spring42is comprised between a first portion (PZ1) of the surface of the hinge (HG6) and a first portion (SC1) of the surface of the hole41. Analogously, the helical spring43is placed in the gap between a second portion (PZ2) of the surface of the hinge (HG6) and a second portion (SC2) of the surface of the hole41. Of course, the use of two springs is not a necessity, one single spring located between a portion (PZ1or PZ2) of the surface of the hinge (HG6) and a portion (SC1or SC2) of the surface of the hole41suffices to accomplish the same effect.

In use, if the tooth30were in one of the two situations shown inFIG. 4or5, a movement of the braking lever14in the direction given by arrow (F8) is possible.

The contact force existing between teeth30and33is then transmitted on the braking lever14, and thus on the helical springs42,43which consequently yield.

Another case occurs when a turning of the driveline gear11, even very small, takes place, thanks to the yielding of the connection, the braking lever14slightly moves following a direction given by an arrow (F8) so that the tooth30exactly engages the gap31between the two teeth32,33.

In a second embodiment of the present invention as shown inFIG. 6, the yielding device40is replaced by an alternative yielding device140. The yielding device140comprises a plate45having a hole41wherein the hinge (HG6) is inserted. Two helical springs42and43position the hinge (HG6) inside the hole41. The plate45of the yielding device140is connected to the frame of the vehicle, while the hinge (HG6) is connected to the braking lever14. When the tooth30is not aligned correctly with the gap31(HG6), the hinge, and thus the braking lever14with the tooth30, will be able to move backward or forward thanks to the springs42and43inside the hole41of the plate45of the yielding device40. Again, only one spring located in the hole41of the plate45suffices to accomplish the same effect.

The main advantage of the above described apparatuses for the aforesaid parking lock consist in a remarkable improvement of the lock steadiness as well as of the security with regard to possible involuntary movements of the vehicle due to its loading. Even if the driveline gear turns a bit, the tooth30and thus the working lever14will be able to move against the force of the springs42,43inside the hole41, such that the forces on the tooth30when contacting the sides of teeth32or33do not rise above the point that the tooth30can break. Additionally, a correct alignment of the tooth30in the hole31is possible and no longer depends of an accidental movement of the driveline gear11.