DESCRIPTION

TECHNICAL FIELD [0001] Described herein are mechanical transmissions comprising a hydraulic clutch for selectively connecting and disconnecting two shafts of the transmission with respect to each other.

BACKGROUND ART

[0002] In many agricultural vehicles it is necessary to connect a drive shaft, such as the power take off of a tractor, to a driven vehicle. In some applications, a clutch that allows the input and the output to be selectively connected and disconnected with respect to each other must be provided along the transmission line. The clutch can be hydraulically operated, i.e. operated through a pressurized hydraulic fluid, which causes engagement of the clutch by pressing two or more friction discs, which are mounted on the input shaft and on the output shaft, against one another.

[0003] In some applications, transmissions with shafts that are coaxial and arranged in line, i.e., in sequence along a shaft line, are used. In these applications it is difficult to insert a hydraulic clutch.

[0004] In other applications, the space available along the transmission line is greatly limited and this causes construction difficulties in producing the collector that supplies the clutch with the hydraulic fluid.

[0005] Therefore, there is a need to produce mechanical transmissions with hydraulic clutches that are capable of solving or reducing at least one of the drawbacks of the prior art. SUMMARY OF THE INVENTION

[0006] According to one aspect, a drive transmission with a hydraulic clutch is provided, said drive transmission being adapted to connect a power take off to a driven vehicle separate from the power take off, wherein the transmission comprises a hydraulic clutch, adapted to connect a power take off to a driven vehicle separate from the power take off. The transmission comprises:

- a first shaft connectable or connected to a joint;

- a second shaft; wherein the first shaft and the second shaft comprise coupling means to the power take off and to the driven vehicle, or vice versa;

- a hydraulic clutch adapted to couple torsionally the first shaft and the second shaft to each other;

- in the hydraulic clutch, a pressure chamber with an atuation member of the clutch controlled by hydraulic fluid fed into the pressure chamber;

- a fluid path having a radial inlet on the first shaft in fluid communication with the pressure chamber;

- an annular collector extending around the first shaft supported rotating on the first shaft through a first support bearing and a second support bearing and having an inlet port for the hydraulic fluid; wherein the annular collector is in fluid communication with the radial inlet of the fluid path on the first shaft; wherein the annular collector is arranged in an intermediate position between the joint and the hydraulic clutch.

[0007] To supply the hydraulic fluid to the clutch, the radial inlet can be in fluid communication with an annular collector forming an annular volume for distribution of the hydraulic fluid.

[0008] In advantageous embodiments, the annular collector comprises a radial inlet, adapted to communicate with a supply line of the pressurized hydraulic fluid.

[0009] Advantageous features and embodiments of the transmission are described below and defined in the accompanying claims, which form an integral part of the present description.

[0010] According to a further aspect, described herein is a system comprising a power take off, for example a power take off of a tractor, a driven vehicle and a transmission as defined above.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The invention will be better understood by following the description and accompanying drawings, which illustrate non-limiting examples of embodiment of the invention. More in particular, in the drawing:

Fig.1 shows a longitudinal section of a drive transmission with a hydraulic clutch in a first embodiment;

Fig.2 shows an enlargement of the collector of the Fig.1 ;

Fig.3 shows a longitudinal section of a drive transmission with a hydraulic clutch in a second embodiment;

Fig. 4 shows an enlargement of the collector of Fig.3; and Fig.5 shows a diagram of a system comprising a tractor, a driven vehicle and a drive transmission.

DETAILED DESCRIPTION OF EMBODIMENTS

[0012] A first embodiment of a drive transmission 1 is illustrated in Figs.l and 2. In particular, Fig.l shows a longitudinal section, i.e., according to a plane containing the rotation axis of the transmission. For simplicity of representation, as the transmission is substantially axially symmetric, the upper part of Fig.1 shows the transmission with the clutch engaged, while the lower part shows the transmission with the clutch disengaged.

[0013] The drive transmission 1 has a first shaft 3, a second shaft 5 and a hydraulic clutch 7, interposed between the first shaft 3 and the second shaft 5. In the illustrated embodiment, the clutch 7, the shaft 5 and the shaft 3 are coaxial to each other and arranged in sequence along the shaft line A-A.

[0014] In the illustrated embodiment, the first shaft 3 is connected to a universal joint 4 and the second shaft 5 is connected to a continuously variable transmission 8.

[0015] The hydraulic clutch 7 comprises an actuation member 13 placed between the end of shaft 5 and the end of shaft 3, and slidingly housed in an axial seat 15. In practice, the actuation member 13 and the axial seat 15 form a piston-cylinder actuator to control engagement and disengagement of the clutch 7, of which the actuation member 13 is the piston and the axial seat 15 is the cylinder. The axial seat 15 and the actuation member 13 define a pressure chamber 17 for the hydraulic fluid of the clutch 7.

[0016] An annular collector 11, shown in greater detail in the enlargement of Fig.2, is provided to feed the hydraulic fluid into the pressure chamber 17. Through the annular collector 11, hydraulic fluid is fed into the pressure chamber 17 along a path 21 comprising a hole 21.1 with an inlet substantially radial with respect to the axis A- A of the transmission 1. The hole 21.1 extends transversely with respect to the axis A- A of the transmission. In the illustrated embodiment, the hole 21.1 is a radial hole. The hole 21.1 is in fluid communication with a hole 21.2 parallel to the axis A-A and preferably coaxial to the axis A-A, which leads into the pressure chamber 17.

[0017] The radial hole 21.1 emerges on the surface of the shaft 3 in an annular volume 23 (see Fig.2), defined between the outer surface of the shaft 3 and an annular body 11.1 of the collector 11. In the illustrated embodiment, the annular volume 23 is delimited by an annular boss 25 formed by the annular body 11.1 of the collector 11 and by an annular boss 27 formed by the shaft 3. The annular bosses 25 and 27 can have conical surfaces facing each other and delimiting the annular volume 23.

[0018] The radial hole 21.1 has an inlet in communication with the annular volume 23, so that pressurized hydraulic fluid, fed through a radial inlet port 29 in the annular body 11.1 of the collector 11, can flow along the path 21 to the pressure chamber 17. The hydraulic fluid is supplied to the port 29 through a line 30 (Fig.l), for example a flexible pipe that can be connected radially to the annular body 11.1 of the collector 11. Annular seals 31 and 33 are provided at the annular bosses 25 and 27 to prevent or limit leakages of hydraulic fluid.

[0019] Two support bearings 35, 37, wherewith the collector 11 is supported on the shaft 3, can be provided externally to the seals 31, 33. In the illustrated embodiment, both the annular seals 31, 33 are housed in annular grooves provided in the annular body 11.1 of the collector 11, so as not to weaken the shaft 3.

[0020] The collector 11 can also be provided with an anti-rotation chain 39 (Fig.1), which holds the collector 11, preventing it from being drawn in rotation by the shaft 3.

[0021] Figs. 3 and 4 illustrate a further embodiment of a drive transmission, indicated with 101.

[0022] In this embodiment, the transmission 101 comprises a first shaft 103 and a second shaft 105 coaxial with each other and arranged in sequence along a shfat line A-A, along which a hydraulic clutch 107 is also arranged. In the configuration of Fig.3, the drive is supplied by a gear box or by a transmission or other mechanical member 109, through a joint 110, for example a universal joint.

[0023] An annular collector 111, which supplies pressurized hydraulic fluid to the clutch 107 to control engagement of the clutch, is arranged on the shaft 103.

[0024] The clutch 107 comprises an actuation member 131 sliding in an axial seat 133. The actuation member 131 and the axial seat 133 form a piston-cylinder actuator for controlling the clutch 107. A pressure chamber into which a hydraulic fluid is fed is indicated with 135.

[0025] The hydraulic fluid is fed into the pressure chamber 135 through a path 141 provided in the shaft 103 and which has an inlet radial with respect to the axis A-A of the transmission. The fluid path 141 has in particular a hole transverse with respect to the axis A-A, for example a radial hole 141.1, in communication with an axial hole 141.2. Through the radial inlet, the fluid path is in communication with an annular chamber or volume 143 of the collector 111, as shown in detail in the enlargement of Fig. 4.

[0026] More in particular, as visible in the detail of Fig.4, the radial hole 141.1 emerges on the surface of the shaft 103 in an annular volume 143 (see Fig.2), defined between the outer surface of the shaft 103 and an annular body 111.1 of the collector 111. In the illustrated embodiment, the annular volume 143 is delimited by an annular boss 145 formed by the annular body 111.1 of the collector 111 and by an annular boss 147 formed by the shaft 103. The annular bosses 145 and 147 can have conical surfaces facing each other and delimiting the annular volume 143.

[0027] The radial hole 141.1 has an inlet in communication with the annular volume 143, so that pressurized hydraulic fluid, fed through an inlet port 149 obtained in the annular body 111.1 of the collector 111, can flow along the path 141 to the pressure chamber 135.

[0028] The inlet port 149 is substantially radial. The hydraulic fluid is supplied to the port 149 through a line 150 (Fig.3), which can also extend radially with respect to the annular body 111.1 of the collector 111. The annular bosses 145 and 147 are provided with annular seals 151 and 153 to prevent or limit leakages of fluid. [0029] In the illustrated embodiment, two support bearings 155, 157, wherewith the collector 111 is supported on the shaft 103, are arranged externally to the seals 151, 153.

[0030] In the illustrated embodiment, both the annular seals 151, 153 are housed in annular grooves produced in the annular body 111.1 of the collector 111, so as not to weaken the shaft 103.

[0031] The collector 111 can also be equipped with an anti -rotation chain 159, which holds the collector preventing it from being drawn in rotation by the shaft 103.

[0032] In the embodiments described above the input and output shafts are coaxial and in line, with the clutch interposed between them. The configuration of the hydraulic fluid supply circuit, with radial inlet and annular collector, represents a particularly effective solution for controlling the clutch in this situation.

[0033] Moreover, the same configuration of the path of the hydraulic fluid and of the annular collector can also advantageously be used in the case in which the input and output shafts are coaxial and concentric, i.e., not in line with each other, but both on the same side of the clutch. In this case the side of the clutch, opposite the input and output shafts, is free and allows front access to the pressure chamber of the hydraulic fluid. In this configuration it would be possible to provide an axial inlet of the hydraulic fluid. However, a solution with radial inlet can be advantageous also in this case, as it can contribute to reducing the overall axial dimension of the transmission. In this case, the clutch can, for example, have a shank coaxial to the input and output axes, positioned on the side of the clutch opposite the input and output shafts. The path of the hydraulic fluid can be produced inside the shank, with an axial hole and a transverse hole, for example radial, that emerges radially on the lateral surface of the shank. The shank can be surrounded by the annular collector, which forms, with the shank, an annular volume or chamber for distribution of the hydraulic fluid. The transverse hole is in fluid communication with the annular volume, which receives the hydraulic fluid through a substantially radial inlet port, produced in the annular body of the collector, which can be in fluid communication with a hydraulic fluid supply line.

[0034] Fig.5 schematically illustrates a system comprising a tractor 101 provided with a power take off, connected to a driven vehicle 102 by means of a transmission line. A transmission with a hydraulic clutch 1 of the type described above is arranged on the transmission line.

[0035] Due to the radial arrangement of the collector that distributes the hydraulic fluid to the clutch, a particularly compact configuration is obtained, in which access to the joints for connection to the power take off and to the driven vehicle is improved and facilitated, even when the spaces available are very limited and without the need to increase the distance between driven vehicle and power take off of the tractor.