The present invention relates to a loading ramp for loading platforms, formed by a frame structure with a bridge plate which at its loading platform edge is pivotally connected to the loading platform and the front edge of which is intended to rest upon the loading floor of a vehicle, with one or more lift cylinders for the raising of the bridge plate, with a feed line for the supply of the pressure medium into the lift cylinder and with a return line for the return flow of the pressure medium out of the lift cylinder, which return line is provided with a valve, whereby, when the valve is opened the pressure medium is allowed to flow out of the lift cylinder through the return line under the weight of the bridge plate, in such a way that the bridge plate can pivot downwards.

Such a loading ramp is known.

With the known loading ramp the front edge of the bridge plate or the front edge of an extendible supporting plate provided on the bridge plate is intended to rest upon the loading floor of a vehicle. When the vehicle is being loaded the vehicle is compressed under the increasing weight and moves down. The bridge plate pivots along with this movement and continues to lean upon the loading floor of the vehicle. In the case of larger vehicles this manner of loading poses no problems.

However, in the case of smaller vehicles, such as small vans, the disadvantage can occur, that the weight of the bridge plate and of the transport means moving over the bridge plate is too heavy for the vehicle.

It is an object of the present invention to provide a loading ramp by means of which this drawback is obviated.

The loading ramp according to the invention to that end is characterized in that the valve comprises a housing provided with a pen, which pen is movable from a first position, in which the pen protrudes out of the housing, into a second position, in which the pen, in part or completely, is countersunk in the housing, whereby, by moving the pen from the one to the other position the valve is opened and closed, while the valve is provided on the loading ramp in such a way, that wl he lxidge

plate comes to rest upon the loading floor of a vehicle, the pen in the housing is moved from the one to the other position, and by means of which the valve is closed, so that no pressure medium can flow out of the lift cylinder and the afore mentioned lift cylinder holds the bridge plate upwards.

According to a characteristic of the loading ramp according to the invention the valve is closed when the pen is in the first position and protrudes out of the housing.

According to a further characteristic of the loading ramp according to the invention, the valve is open when the pen is in the second position and is countersunk in the housing.

According to another characteristic of the loading ramp according to the invention the pen is a spring loaded pen, whereby the pen can be pushed against spring force from the first position into the second position.

According to yet another characteristic of the loading ramp according to the invention at the front edge of the bridge plate a frame with a supporting plate is provided, which frame is extendible in the horizontal direction, while the supporting plate is intended to rest with its front edge upon the loading floor of a vehicle, whereby the frame is supported at one or both sides at a pivoting point in the frame structure, whereby the frame can pivot along the pivoting point from a position in which the front edge of the frame is inclined downwards and the rear edge is inclined upwards to a position in which the front edge is inclined upwards and the rear edge is inclined downwards, and by means of which pivoting of the frame the pen is moved into and out of the housing of the valve.

According to a characteristic of the loading ramp according to the invention when the frame is pivoted into a position in which the front edge of the frame is inclined downwards and the rear edge of the frame is inclined upwards, the afore mentioned rear edge of the frame pushes the pen into the housing of the valve, and thereby into the second position, such that the valve is opened.

According to yet a further characteristic of the loading ramp according to the invention when the frame is pivoted into a position in which the front edge of the frame is inclined upwards and the rear edge of the frame is inclined downwards, in between the afore mentioned rear edge of the frame and the housing of the valve a space is present, such that the pen protrudes out of the housing of the valve, and thereby is in the first position, such that the valve is closed.

With the loading ramp according to the invention it is achieved that, when the bridge plate with the wholly or partly extended frame with the supporting plate is placed onto the loading floor of a vehicle and comes to rest there upon, the pen in the valve is moved in the first position whereby the valve is closed. No pressure medium can flow out of the lift cylinder, so that the lift cylinder maintains the bridge plate in an upwards position. The weight of the bridge plate and of any transport means moving over the bridge plate are not borne by the vehicle but by the lift cylinder.

Further characteristics and particulars will be described with reference to the drawings of an example of an embodiment.

Figure 1 shows in section a side view of an example of an embodiment of the loading ramp according to the invention.

Figure 2a shows in section a part of a side view of an example of an embodiment of the loading ramp according to the invention.

Figure 2b shows enlarged a detail of figure 2a.

Figure 3 shows a perspective view of an example of an embodiment of a valve as this is applied in the invention.

The figures 4 and 5 show a hydraulic diagram, whereby figure 4 relates to a system as this is applied with smaller vans, and whereby figure 5 relates to a system as this is applied with large trucks.

In the figures 1 and 2 a loading ramp is shown, formed by a frame structure 2 with a bridge plate 3 which at its loading platform edge 4 is pivotally connected to the loading platform 5. At the front edge of the bridge plate 3 an extendible frame 6 with at its front edge a supporting plate 7 is provided, which is intended to rest upon the loading floor 8 of a vehicle.

Further is shown in figure 1 a lift cylinder 9 for the raising of the bridge plate 3.

Further are provided a feed line (not shown in the drawing) for the supply of the pressure medium into the lift cylinder 9 and a return line (not shown in the drawing) for the return flow of the pressure medium out of the lift cylinder 9, which return line is provided with a valve 10 (see figure 2a). When the valve 10 is opened the pressure medium can flow out of the lift cylinder 9 through the return line under the weight of the bridge plate 3, in such a way that the bridge plate can pivot downwards. As can be seen in figures 2a and 2b, the valve 10 comprises a housing 11 which is provided with a pen 12. The pen 12 can be pushed from a first position, in which the pen 12 protrudes out of the housing 11, into the housing 11 into a second position, in which the pen 12 completely or almost completely is countersunk in the housing 11. The valve 10 is carried out in such a way that by moving the pen 12 from the one to the other position the valve 10 is opened and closed. In this example of an embodiment of the loading ramp according to the invention the valve 10 is carried out such that it is open when the pen 12 is in the second, pushed in, position and it is closed when the pen 12 is in the first position and protrudes out of the housing 11.

The pen 12 is a spring loaded pen, so that the pen 12 can be pushed against spring force from the first position into the second position, and springs back when the pen is no longer pushed inside any more.

The frame 6 is supported at one or both side edges 13 at a pivoting point 14 in the frame structure 2, whereby the frame 6 can pivot along the pivoting point 14 from a position in which the front edge 15 of the frame 6 is inclined downwards and the rear edge 16 of the frame 6 is inclined upwards to a position in which the front edge 15 of the frame 6 is inclined upwards and the rear edge 16 of the frame 6 is inclined downwards. Thereby the path of movement upwards of the front edge 15 of the frame 6 is limited by the front edge 17 of the bridge plate 3, against which the upper side of the front edge 15 of the frame 6 comes into contact. As can be seen more in particular in figure 3, the path of movement upwards of the rear edge 16 of the frame 6 is limited by the valve 10 provided to a part 18 of the frame structure. As can be seen in figure 3, on its movement upwards (see arrow) the rear edge 16 of the frame pushes the pen 12 into the housing 11 of the valve 10.

When the loading ramp with the supporting plate 7 does not rest upon the loading floor 8 of a vehicle, the front edge 15 of the frame 6 is inclined downwards because it is not supported from underneath, and the rear edge 16 of the frame 6 is inclined upwards. In this position the rear edge 16 pushes the pen 12 into the housing 11 in the second position so that the valve 10 is open. The pressure medium can flow out of the lift cylinder 9 through the return line under the weight of the bridge plate, and the bridge plate 3 can move down.

When the supporting plate 7 comes to rest upon the loading floor 8 of a vehicle, the frame 6 will pivot through the pivoting point 14 with its front edge 15 upwards until the front edge 15 of the frame 6 touches against the front edge 17 of the bridge plate 3.

The front edge 15 of the frame 6 cannot move upwards further because it is held back by the front edge 17 of the bridge plate. The rear edge 16 of the frame pivots downwards, which creates a space 19 between the rear edge 16 of the frame and the pen 12. Because of this the pen 12 is no longer pushed into the housing 11 by the rear edge 16, so that the pen 12 springs outwards. Because of this, the valve takes in the first position and the valve is closed and the flowing out of the pressure medium out of the lift cylinder 9 through the return line is stopped and with that the downwards movement of the bridge plate 3 is stopped.

In figure 2a this small tilting movement of the frame 6 is indicated with the capital letter"A", while in figure 2b it is further indicated that the movement"A"of the frame gives a movement"a", which movement"a"is divided in a movement"s" (the stroke of the pen 14 or the valve). As soon as gap"g"comes about the valve is closed, and the flowing out through the return line of the pressure medium out of the lift cylinder 11 and with that the downwards movement of the bridge plate 3 is stopped.

The figures 4 and 5 show a hydraulic diagram, whereby figure 4 relates to a system as this is applied with smaller vans, and in which figure 5 relates to a system as this is applied with large trucks.

Figure 4. Small vans.

In the application for small vans it pertains to the downwards movement.

l. Hereby the valve 2 is always open.

2. Valve 3 and 4 are then closed.

3. Lift cylinder 2 and valve 8 show the downwards movement. The front edge or rather lip of the supporting plate is not yet in contact with the floor of the van. Oil flows out of the lift cylinder to the oil tanlc, through valve 6, 8 and 2.

4. Lift cylinder 1 and valve 7 show that the movement has stopped; valve 7 is closed.

5. In this situation only the weight of the part of the lip, due to the centre of gravity which is slightly before the pivoting point, rests upon the floor of the small van (the force that is required to stop the downwards movement of the loading ramp). The remainder of the weight, including the transport means, is borne by the lift cylinders (bridge plate, supporting plate, remainder of the lip and the transport means, as long as the transport means still stands on the bridge plate or the supporting plate.) Figure 5. Large trucks.

In the application for large trucks it also only pertains to the downwards movement. l. Valve 2,3 and 4 are always open.

2. Valve 7 and 8 do not have a function anymore; the oil can flow through the valves 3 and 4.

3. The downwards movement is stopped by the loading floor of the truck. The full weight of the platform, the lip or supporting plate and the transport means rest upon the floor of the truck.

The invention is not limited to the example of the embodiment described above.

In the example of the embodiment described above the valve is fixedly mounted to the bridge plate or the frame structure of the loading ramp. The frame tilts relative thereto and by this movement the pen is moved into and out of the housing of the valve and the valve is thereby opened and closed. The other way round it is also possible to mount the valve onto the movable frame, whereby, by the movement of the frame the valve is brought into contact with a fixed frame structure part and by means of which the valve can be operated.