Patent Description:
In the field of goods transport vehicles, it is known to associate a tailgate lift comprising a mobile platform to the vehicle to facilitate operators in the loading and unloading of goods.

The tailgate lift is actuated by a plurality of hydraulic actuators that determine its movement between a vertical transport position and a tailgate position on the ground. Among the tailgate lifts known in the prior art, tailgates having an articulated parallelogram type structure are known. These tailgates provide for both an opening/closing rotation movement that brings the platform from the vertical transport position to a horizontal position in which the platform is at the height of the loading plane of the vehicle, and vice versa, and a lifting/lowering translational movement between this position and a horizontal tailgate position on the ground, during which the platform translates parallel to the ground.

These tailgates then provide for a ground connection movement, in which the platform passes from the horizontal position to an inclined position, and vice versa; in which in this inclined position the end edge furthest from the vehicle is in contact with the ground to allow operators to load/unload goods, for example through the use of pallet trucks. This movement, unlike the opening/closing rotation movement, must take place at a controlled desired speed, suitably limited, because the ground connection movement takes place when the platform must withstand a certain load, even of several tons.

Hydraulic actuators usually comprise a first pair of actuators and a second pair of actuators, one arranged on the right side and one on the left side of the chassis. Each pair of actuators comprises a rotation actuator, configured to determine said rotation movement of opening/closing of the platform, and a lifting actuator, configured to determine said translational movement of lifting/lowering.

The movement of the known tailgate lifts can be obtained by means of a control that can be electronic, mechanical or hydraulic.

Usually, when the vehicle to which the tailgate lift is to be connected is a truck having a mass of <NUM> to <NUM> tons, the hydraulic actuators are controlled by means of an electronic type control or by means of a mechanical type control.

In the case of electronic control, the driver of the vehicle is not able to carry out quick and simple repairs, but any failure of electronic components forces them to contact specialized centres equipped with the necessary tools to perform the control diagnostics and the necessary corrective actions to restore the operation of the tailgate. This leads both to the dissatisfaction of the driver of the vehicle, and to rather high maintenance times and costs, which also impose a period of inactivity on the vehicle.

A further shortcoming of electronic control is that it does not have adequate reliability. In fact, different electronic components can be subject to malfunctions, possibly caused by external environmental conditions, for example humidity, which can damage some components.

It is clear that incorrect operation of these components can have very serious consequences on the safety of operators and goods handled. For example, if a sensor communicates that the tailgate has reached the ground and therefore starts the ground connection movement even when in fact the tailgate is still far from the ground, it is clear that this could be dangerous for the operators and damaging to the goods being handled.

Another shortcoming of the electronic control is the fact that it necessitates further additional solutions, to determine the necessary slowing of the ground connection movement, for which it is necessary to introduce a complex valve system to reduce the flow of oil into/out of the rotation actuator.

The mechanical control of the movement of the actuators allows some shortcomings of the electronic control to be overcome, but has the shortcoming of including a plurality of levers and other mechanical members that can operate correctly only if the centre distances between the load-bearing members of the tailgate between the right side and the left side are fixed and connected to each other. In other words, the mechanical control can only be used if the tailgate is connected to the vehicle along its entire transverse length, which goes from the right side to the left side. There are some solutions in the art in which the tailgate is connected to the vehicle only in some localized points; solutions that are not compatible with the mechanical control of the actuators. <CIT> discloses a tailgate lift similar to the preamble of claim <NUM>.

One purpose of the present invention is to provide a tailgate lift for a vehicle whose maintenance is simple, fast and economical.

Another purpose of the invention is to provide a tailgate lift that is safe and reliable, capable of maintaining a safe condition in the event that a malfunction is detected, for example in the event of a breakage of a pipe, or a condition caused by the unbalancing of the load on the platform, so as to avoid damaging the goods to be handled and above all, to avoid injuring persons in the vicinity. Another purpose of the invention is to provide a control of the actuators that move the tailgate lift that is exclusively hydraulic.

According to one aspect of the invention, a tailgate lift for a vehicle is provided, in accordance with the features of claim <NUM>.

These and other aspects, characteristics and advantages of the present invention will become apparent from the following description of some embodiments of a lift device for a vehicle according to the invention, given as a non-restrictive example with reference to the attached drawings wherein:.

With reference to <FIG>, a tailgate lift <NUM> according to the present invention is configured to be associated to a vehicle <NUM>, partially and schematically illustrated in the figure.

Preferably, the vehicle <NUM> is a truck of less than eight tons in size, preferably between <NUM> and <NUM> tons in size.

The tailgate <NUM> comprises a loading platform P configured to receive the goods to be loaded or unloaded onto/from the vehicle <NUM>. The platform P defines a proximal end edge P1 and a distal end edge P2 with reference to a chassis <NUM> of the vehicle <NUM>. In correspondence with the proximal end edge P1, the platform P comprises two ground rest elements <NUM>, one arranged on the right side and one arranged on the left side of the vehicle <NUM>.

The tailgate <NUM> also comprises two support members <NUM> configured to support a transverse bar <NUM>, which acts as a bumper and is therefore configured to absorb the energy generated during a collision or an impact.

As will become clearer from the following detailed description, the transverse bar <NUM> also performs a structural support function for the tailgate <NUM>.

The tailgate <NUM> comprises connection means <NUM> which connect it to the chassis <NUM> of the vehicle <NUM> by means of any known fastening member. These connection means <NUM> include suitable mechanical connection members, such as brackets, plates, crossbeams, which are fixed to the chassis <NUM> in any appropriate known manner, typically by bolting.

In the example illustrated, the connection means <NUM> comprise a right anchoring bracket <NUM> and a left anchoring bracket <NUM>, respectively fixed to the right and left side of the chassis <NUM>.

The right anchoring bracket <NUM> and the left anchoring bracket <NUM> are separate and spaced apart from each other, each being independently connected to the chassis <NUM>.

The tailgate <NUM> also comprises a lifting actuator <NUM> and a rotation actuator <NUM>, both connected to the connection means <NUM> at the respective end thereof.

Both the lifting <NUM> and rotation <NUM> actuators are hydraulic actuators wherein the operating fluid is an oil suitable for industrial uses.

In the example provided herein, the lifting actuator <NUM> is disposed on the left side of the vehicle <NUM>, and is thus connected to the left anchoring bracket <NUM>, while the rotation actuator <NUM> is disposed on the right side of the vehicle <NUM>, and is thus connected to the right anchoring bracket <NUM>.

Compared to the solutions known in the art, which comprise two pairs of actuators, one on the right and one on the left, each comprising both a lifting actuator and a rotation actuator, the tailgate <NUM> according to the present invention comprises only one pair of actuators, making it cheaper and lighter than the known solutions.

The tailgate <NUM> comprises a pair of arms <NUM>, arranged with one on the right side and the other on the left side of the vehicle <NUM>.

Each arm <NUM> is pivoted on the connection means <NUM> at a first end thereof. The arm <NUM> disposed on the right side is pivoted on the right anchoring bracket <NUM>, while the arm <NUM> disposed on the left side is pivoted on the left anchoring bracket <NUM>.

The platform P is pivoted on the pair of arms <NUM>, in correspondence with their respective second ends, opposite said first ends.

In the example provided here, the platform P is pivoted on the arms <NUM> in correspondence with a first connection zone <NUM>, defined in the ground rest elements <NUM>.

It is noted that, for correctly moving the platform P, the lifting actuator <NUM> is connected, on the opposite side with respect to the left anchoring bracket <NUM>, to the arm <NUM> in a correspondence with a further connection area <NUM>', while the rotation actuator <NUM> is connected, on the opposite side with respect to the right anchoring bracket <NUM>, to the platform P, in a second connection area <NUM>, defined in correspondence with the ground rest elements <NUM>.

Since the connection of the platform P to the chassis <NUM> of the vehicle <NUM> takes place through the pair of arms <NUM> in correspondence with the two different anchoring brackets <NUM> and <NUM>, right and left, different and not connected to each other, and since only a lifting actuator <NUM> and a rotation actuator <NUM> are provided, arranged one on the right side and one on the left side of the vehicle, it is evident that the transverse bar <NUM> acts as a structural connection between the pair of arms <NUM> homogeneously transmitting the movement determined by the lifting actuator <NUM> between the two sides, right and left, of the vehicle <NUM>. In this way the transverse bar <NUM> allows the torque that is generated to be transmitted from one side to the other of the vehicle <NUM>.

In the example described here, the lifting actuator <NUM> is a single-acting cylinder while the rotation actuator <NUM> is a double-acting cylinder, as will also be clear from the following description of a possible example of a hydraulic circuit <NUM> for driving such actuators.

The tailgate <NUM> also comprises a compensation actuator <NUM>, or auxiliary actuator for the ground connection of the platform P, the function of which will be described in detail below, within the scope of the description of the operation of the tailgate <NUM>.

The compensation actuator <NUM> is in fluid communication with both the lifting actuator <NUM> (bottom side) and the rotation actuator <NUM> (rod side), as explained in detail below. In the example provided herein, the compensation actuator <NUM> is disposed on the left side of the vehicle <NUM>, associated to the lifting actuator <NUM>. In another version, not shown, the compensation actuator <NUM> can be arranged on the right side of the vehicle, being associated to the rotation actuator <NUM>.

The fact that the compensation actuator <NUM> is directly associated to one of the lifting actuator <NUM> and the rotation actuator <NUM> avoids duplication of the flexible rubber ducts that transfer the oil under pressure between these actuators, reducing the risk of breakages, which can cause malfunctions of the tailgate <NUM>.

The platform P is movable between a closed transport position T, in which the platform <NUM> is arranged vertically (<FIG>), i.e. substantially perpendicular to the ground, to a position E of the tailgate with respect to the ground, in which it is arranged substantially horizontal (<FIG>) and close to the ground. In this position, the platform P rests on the ground only by means of the ground rest elements <NUM>.

To pass from said closed transport position T to said position of the tailgate with respect the ground, the platform P transits in a position horizontal to the loading plane L (<FIG>), in which it is horizontal, and arranged substantially at the same height as the loading plane of the vehicle <NUM>. When the platform P passes from said position L horizontal to the loading plane (<FIG>) to said position of the tailgate with respect to the ground E (<FIG>), it remains substantially horizontal, i.e. substantially parallel to the ground during said movement.

In order to be able to load and unload the goods from the platform P, the latter must be brought from said position of the tailgate with respect to the ground, to a position I of connection to the ground (<FIG>), in which the distal end P2 of the platform P is in contact with the ground so that the platform P is inclined by a certain angle α with respect to a horizontal plane.

With particular reference to the hydraulic diagram of <FIG>, a hydraulic actuation circuit <NUM> of the lifting, rotation and compensation actuators <NUM>, <NUM>, <NUM> will now be described. The tailgate <NUM> comprises a pump <NUM>, driven in a known manner by a motor <NUM>, a filter F and a plurality of valves, suitably located in the circuit <NUM>, and described in detail below.

The circuit <NUM> comprises a delivery branch <NUM> on which a one-way valve <NUM> and a distributor valve <NUM> are arranged. In the example illustrated here, said distributor valve <NUM> is a four-way, two-position solenoid valve.

On this delivery branch <NUM> there is also a maximum pressure valve PMAX, which is a safety valve that intervenes if the pressure on this branch reaches a predetermined maximum pressure, for example equal to <NUM> bar, in order to prevent dangerous malfunctions from occurring if this pressure is exceeded.

The delivery branch is divided into a first connection branch <NUM>, which reaches the lifting actuator <NUM>, in particular the bottom side chamber of the latter, and into a second connection branch <NUM>, which reaches, instead, the lifting actuator <NUM>, in particular the bottom side chamber of the latter.

Both on the first and on the second connection branch <NUM>, <NUM> there are arranged in succession: a shutter solenoid valve <NUM>, which alternatively allows or prevents the passage of oil, and a flow limiting valve <NUM>, configured to control the flow rate of the oil, at least in a selected direction. The compensation actuator <NUM> is connected to the lifting actuator <NUM> via a third connection branch <NUM> and to the rotation actuator <NUM> via a fourth connection branch <NUM>. It should be noted that in the illustrated example, in which the compensation actuator <NUM> is fixed to the lifting actuator <NUM>, the third connection branch <NUM> can be represented by one or more rigid fittings, since the two cylinders are joined, while the fourth connection branch <NUM> can be a flexible pipe, for example made of rubber.

In particular, the third connection branch <NUM> connects the bottom side chamber of the compensation actuator <NUM> with the bottom side chamber of the lifting actuator <NUM>, and the fourth connection branch <NUM> connects the rod side chamber of the compensation actuator <NUM> with the bottom side chamber of the rotating actuator <NUM>.

An interception valve <NUM> is provided, configured to allow or prevent the passage of oil flow from the compensation actuator <NUM> to the rotation actuator <NUM>, or vice versa. This interception valve <NUM> is integrated in the rotation actuator <NUM>, in particular in its bottom, as indicated by the dashed box in the figure.

As schematized in <FIG> with a dashed line box surrounding both the lifting actuator <NUM> and the rotation actuator <NUM>, the shutter valves <NUM> and flow restrictor valves <NUM> are also integrated in these actuators, being for example integrated in the respective bottoms or in the respective side sleeves.

The interception valve <NUM> is disposed on the fourth connection branch <NUM>. Such a position increases the safety of the circuit <NUM> since the interception valve <NUM> is controlled by a position sensor associated to the arm <NUM> set so as to keep it closed until it reaches the vicinity of the ground. In this way, even if there is a break or a leak in correspondence with the flexible pipe that defines the fourth connection branch <NUM>, the platform P immediately touches the ground, but since it is already in its vicinity, this movement, although sudden and uncontrolled, does not cause damage to the goods handled and/or to the operator due to the short stroke.

In another embodiment, a further interception valve, similar to the valve <NUM>, could also be provided on the third connection branch <NUM>, if it was also configured as a flexible pipe. In the example provided here, such a further valve would however be superfluous since there is substantially a direct connection between the actuators <NUM> and <NUM>.

The circuit <NUM> includes a further branch <NUM> that flows into the rod side chamber of the rotation actuator <NUM>. In correspondence with a node N, the further branch <NUM> bifurcates into two forks: a first fork 36a which in a certain position of the valve <NUM> can be connected to the delivery branch <NUM> on which the pump <NUM> is arranged, and another fork 36b which reaches directly to the tank.

The following describe an operating cycle of the platform P via the circuit <NUM>.

Initially the platform P is in the closed transport position T.

To rotate the platform P to the position L horizontal to the loading plane, the diverter valve <NUM> is energized to be brought to the position such that the oil, after traversing the delivery branch <NUM> and the first fork 36a of the further branch <NUM>, reaches the rod-side chamber of the rotation actuator <NUM> so as to retract the rod and determine the opening of the platform P. At the same time, the shutter solenoid valve <NUM> arranged on the first communication branch <NUM> is kept closed, while the shutter solenoid valve <NUM> arranged on the second communication branch <NUM> is opened to allow the discharge of the oil from the bottom side of the rotation actuator <NUM>.

When the platform P passes from the position L horizontal to the loading plane to the horizontal position E in which the tailgate is on the ground, the shutter solenoid valve <NUM> on the second connection branch <NUM> is closed, while that on the first connection branch <NUM> is opened to allow the oil to exit from the chamber on the bottom side of the lifting actuator <NUM>. In this configuration, the diverter valve <NUM> remains energized to maintain the configuration described above.

The oil outlet from the bottom side chamber of the lifting actuator <NUM> is determined by the weight of the platform P and any load disposed thereon, which retracts the rod of the lifting actuator <NUM>. The rate of descent is controlled by the calibration of the flow limiting valve <NUM> and descent ceases when the ground rest elements <NUM> reach the ground, at which time the pressure in the bottom side chamber of the lifting actuator <NUM> reaches zero.

The movement of the platform P between the horizontal position E in which the tailgate is on the ground and the position I of connection to the ground is obtained by the transfer of oil between the compensation actuator <NUM> and the rotation actuator <NUM> through the second communication branch <NUM>. Whether the oil flow is from the compensation actuator <NUM> to the rotation actuator <NUM>, or vice versa, is determined by the position of the valves <NUM>, <NUM>, <NUM> and of course by whether or not the pump <NUM> is actuated.

This system causes the same amount of oil necessary to reach the position I of connection to the ground to then return through the reverse path to allow the horizontal position E in which the tailgate is on the ground to be reached. The geometric dimensions of the compensation actuator <NUM>, in particular the diameter of the rod and therefore the ratio between the useful thrust areas from the two opposite parts of the piston, are such as to manage the pressures so that it can operate correctly as described herein.

In particular, when the platform P moves from the horizontal position E in which the tailgate is on the ground the position I of connection to the ground, the diverter valve <NUM> is switched by the aforementioned position sensor to cause the oil from the bottom-side chamber of the rotation actuator <NUM> to pass to the rod-side chamber of the compensation actuator <NUM>. In this configuration the shutter solenoid valve <NUM> on the first connection branch <NUM> is open while the shutter solenoid valve <NUM> on the second connection branch <NUM> is closed, and the diverter valve <NUM> is switched to remain in the position described above throughout the opening and lowering movement of the platform P.

Conversely, when the platform P is to be lifted and closed, it is first necessary to move the platform P from the position I of connection to the ground to the horizontal position E in which the tailgate is on the ground. To do this, the diverter valves <NUM> remain in the configuration just described, the pump <NUM> is activated, and the diverter valve <NUM> is in the rest position illustrated in <FIG> to cause the pump <NUM> to send oil to the bottom side chambers of the lifting actuators <NUM> and compensation actuators <NUM>. Since the circuit is designed so that the oil encounters fewer pressure drops to reach the latter, it will first enter the bottom side chamber of the compensation actuator <NUM> along the third connection branch <NUM>. This causes oil to exit from the rod side chamber of the compensation actuator <NUM>, which oil enters the bottom side chamber of the rotation actuator <NUM>. This causes the rod of the latter to come out, which causes the platform P to reach the horizontal position E in which the tailgate is on the ground. Continuing to send oil, once the compensation actuator <NUM> has reached the end of its stroke, the rotation actuator remains stationary in the position it has reached, and the oil enters the chamber on the bottom side of the lifting actuator <NUM>, thus starting the lifting of the platform P from the horizontal position E in which the tailgate is on the ground to the position L horizontal to the loading plane.

For the closing rotation movement of the platform P, the valve <NUM> remains in the configuration described above (i.e. that which can be seen in <FIG>), the shutter valve <NUM> on the second connection branch <NUM> is opened, while the shutter valve <NUM> on the first connection branch <NUM> is opened so that the oil reaches only the chamber on the bottom side of the rotation actuator <NUM>, determining the exit of the respective rod.

It should be noted that all movements of the platform P are controlled by exclusively hydraulic actuators. This eliminates, or at least significantly reduces, the electrical or electronic components of the tailgate <NUM>, increasing its reliability and reducing its complexity and cost.

It has been found in practice that the invention achieves the intended purposes.

Claim 1:
Tailgate lift (<NUM>) for a vehicle (<NUM>) comprising:
- a loading platform (P),
- a pair of support arms (<NUM>) which connect said platform (P) to a chassis (<NUM>) of said vehicle (<NUM>),
- means (<NUM>, <NUM>) for moving said platform (P), comprising a lifting actuator (<NUM>) and a rotation actuator (<NUM>), which are configured to give said platform (P) a vertical translation movement, in which said platform (P) translates disposed horizontally, that is, parallel to the ground, and a rotation movement, respectively,
- a transverse bar (<NUM>) attached to said pair of support arms (<NUM>) by means of support members (<NUM>),
said tailgate (<NUM>) is characterized in that one support arm of said pair of support arms (<NUM>) and one of either said lifting actuator (<NUM>) or said rotation actuator (<NUM>) are connected to said chassis (<NUM>) in correspondence with a right anchoring bracket (<NUM>), while the other support arm of said pair of support arms (<NUM>) and the other of either said lifting actuator (<NUM>) or said rotation actuator (<NUM>) are connected to said chassis (<NUM>) in correspondence with a left anchoring bracket (<NUM>), which is separate and independent from said right anchoring bracket (<NUM>), wherein said transverse bar (<NUM>) structurally connects said pair of support arms (<NUM>), and in that it also comprises a compensation actuator (<NUM>) configured to move said platform (P) between a horizontal position (E) in which the tailgate is on the ground and a position (I) of connection to the ground, in which said platform (P) is inclined by a determinate angle (α) with respect to the horizontal plane.