The present invention pertains to a pump device for a power take-off according to the preamble to claim 1 , a power take-off for a take-off module according to the preamble to claim 8, a take-off module according to the preamble to claim 1 1 , and a vehicle comprising a power take-off according to the preamble to claim 13.

Sometimes trucks are equipped with different types of auxiliary units. Such auxiliary unit may e.g. consist of cranes and compressors. In order to operate the auxiliary units, power is taken from the truck's driveline with the help of one or several power take-offs. A common name for such power take-offs is PTO, an abbreviation of

Power Take-Off. PTOs may be connected to and mounted on basically all the components of the driveline, e.g. on the engine, on the gearbox or between the engine and the gearbox. In order to operate an auxiliary unit in the form of a crane with hydraulic cylinders, pressurised hydraulic oil is required, which is why a take-off module in the form of a hydraulic pump is assembled in the PTO. If the auxiliary unit is a compressor, a take-off module in the form of a connecting flange is preferably assembled in the PTO, to which connecting flange the compressor's input shaft is connected. A power take-off may be single or double, and may be direct drive or clutched. The direct drive PTOs are operated directly by the vehicle's driveline and the clutched are operated via a transmission, in order to up-shift the engine speed. The double PTOs comprise an in-built transmission, distributing the power to two sockets for connection of take-off modules.

The moving components of the PTOs and take-off modules depend on lubrication in order to function satisfactorily. Different types of lubricating systems for PTOs and modules are available. One type of lubricating system is splash lubrication, where the lubricant oil, which is trapped in the house of each PTO and take-off module, is circu- lated with the help of the moving components in the PTO and the take-off module. In splash lubrication the lubricating effect is restricted by the rotation speed of the moving components, which entails that pressure-lubricated bearings may not be used in the PTO or the take-off module. In another type of existing lubricating systems, the internal lubricating system of the gearbox is used, so that transmission oil is pressurised in the gearbox and led to the PTO and the take-off module. The drawback, however, is that the flow and the pressure of the lubricant oil decrease in the components to be lubricated in the gearbox, since part of the flow and the pressure is distributed to the PTO and the take-off module.

There are PTOs containing a separate lubricating system with a pump device, supplying the PTO and the take-off module with lubricant oil flow and lubricant oil pressure. Document US5092736 shows a pump device for a PTO, which pump device is arranged on a drive shaft for the PTO. Such a separate pump device for the PTO and the take-off module requires power transmitted from the drive shaft, which entails increased fuel consumption in the vehicle on which the PTO is mounted. In case the vehicle is equipped with such a PTO, but no take-off module is mounted on the PTO, fuel will be consumed unnecessarily, since the pump device is operated and power is required to pump lubricant oil with the pump device.

SUMMARY OF THE INVENTION Despite prior art solutions, there is a need to develop a pump device for a PTO that saves fuel, does not impact the ordinary oil system in a vehicle driveline, enables the use of pressure-lubricated bearings, and allows for forced oil cooling of the PTO.

The objective of the present invention is thus to provide a pump device for a PTO that saves power when the PTO is not used.

Another objective of the invention is to provide a pump device for a PTO that does not impact the ordinary oil system in a vehicle driveline. Another objective of the invention is to provide a pump device for a PTO that facilitates the use of pressure-lubricated bearings in the PTO and in a take-off module connected to the PTO. Another objective of the invention is to provide a pump device for a PTO, allowing for forced oil cooling of the PTO.

These objectives are achieved with a pump device of the type specified at the beginning, which is characterised by the features specified in claim 1 .

Such a pump device for a PTO will save fuel, not impact the ordinary oil system in a vehicle driveline, facilitate the use of pressure-lubricated bearings and allow for forced oil cooling of the PTO, since the oil transports away heat developed in the PTO.

According to one embodiment, the switching element is axially shiftable. Thus, the switching element may easily be switched between the first and the second state.

According to another embodiment, the switching element is a disc spring, which in the first state takes on a cupped shape, and in the second state takes on a substantially plane shape. A disc spring has a simple construction, whose change in shape between the first and the second state is used.

According to another embodiment, the disc spring is arranged to be moved to the second state by overcoming the spring force of the disc spring. The disc spring's spring force may be easily adapted to the intended purpose through choice of material and shape.

According to another embodiment, the house forms a PTO for a take-off module. The shape of the house may thus be adapted to collaborate with the shape of the take-off module.

According to another embodiment, the drive element is an output shaft from a gearbox. By arranging the PTO at the gearbox, a component rotating in the gearbox may be used for connection of a shaft for operation of a take-off module connected to the PTO.

According to another embodiment, the drive element comprises a coupling sleeve for connection of a coupling shaft in a take-off module. The coupling sleeve may be easily designed to take on a shape suitable for, and collaborating with, the take-off module.

The objectives specified above are achieved also with a PTO of the type mentioned above, which is characterised by the features specified in claim 8.

According to one embodiment, the house comprises axially oriented bores, partly designed to receive a means of control for the switching element and partly to form channels for the flow of fluid. By designing the house with axially oriented bores, con- trol means arranged on the take-off module may impact the switching element, so that it switches between the first and the second state. The bores that do not receive a control means will function as inlets and outlets for fluid between the PTO and the take-off module. According to another embodiment, the drive element comprises a coupling sleeve for connection of a coupling shaft in the take-off module. Thus, the coupling sleeve may be easily designed to take on a shape suitable for, and collaborating with, the take-off module. The objectives specified above are achieved also with a take-off module of the type mentioned above, which is characterised by the features specified in claim 1 1 .

According to one embodiment, the control element is a spigot, which extends substantially in parallel with a coupling shaft of the PTO. Thus, the switching element may easily be switched between the first and the second state when the take-off module is removed or mounted on the PTO, respectively.

The objectives specified above are achieved also with a vehicle of the type mentioned above, which is characterised by the features specified in claim 13. Other advantages of the invention are set out in the detailed description below. BRIEF DESCRIPTION OF THE DRAWINGS

Below is a description, as an example, of preferred embodiments of the invention with reference to the enclosed drawings, in which:

Fig. 1 shows in a side view a schematically displayed vehicle with a pump device for a PTO according to the present invention,

Fig. 2 shows a cross-sectional view of a schematically displayed PTO with the pump device according to the present invention, Fig. 3 shows a plane view of the PTO according to the present invention,

Fig. 4 shows a cross-sectional view along the line I - 1 in Fig. 2, and

Fig. 5 shows a cross-sectional view of a schematically displayed PTO with the pump device according to the present invention, with a connected take-off module.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

Fig. 1 shows a schematic side view of a vehicle 1 , comprising a driveline 2 with a combustion engine 4, which is connected to a gearbox 6. The gearbox 6 is also connected to the driving wheels 8 of the vehicle 1 . The vehicle 1 is equipped with a crane 10, in which a hydraulic cylinder 12 is arranged. A take-off module 14 in the form of a hydraulic pump is arranged to operate the hydraulic cylinder 12, and thus the crane 10. The hydraulic pump 14 is connected to a PTO 16, which is arranged at the driveline 2 of the vehicle 1 . The hydraulic pump 14 is connected to the hydraulic cylinder 12 via hydraulic conduits. The PTO 16 comprises a pump device 22 according to the present invention. Fig. 2 shows a schematic sectional view of a PTO 16 according to the present invention. The PTO 16 comprises a house 18, which at least partly contains a drive element 20 in the form of an output shaft 20 from the driveline 2, a coupling sleeve 24, connected to the output shaft 20, and a first bearing 26, bearing the coupling sleeve 24 in the house 18. The house 18 is designed to form a socket for the take-off module 14. The PTO 16 also comprises the pump device 22, operated by the output shaft 20. The output shaft 20 is intended to be connected to the driveline 2 of the vehicle 1 (Fig. 1 ), so that the driveline 2 operates and brings the pump device 22 to pump fluid, e.g. transmission oil, from the gearbox 6. In case the PTO 16 is arranged at the gearbox 6 of the vehicle 1 , the output shaft 20 is connected to a rotatable shaft (not shown) in the gearbox 6. The output shaft 20 is stored in the gearbox 6 with a second bearing 28. The coupling sleeve 24 comprises means, e.g. a spline 30, for connection with the output shaft 20 and for connection of the take-off module 14. The pump device 22 comprises a fluid inlet 32 and a fluid outlet 34. A hose or a pipe conduit 36, leading transmission oil from the gearbox 6, is connected to the fluid inlet 32. A lid 39, through which the hose or the pipe conduit 36 extends and is connected, abuts on one side of the pump device 22. Preferably, the PTO 16 is connected with the gearbox 6 through mounting bolts 38. In the pump device 22, the fluid inlet 32 and the fluid outlet 34 are connected with a rotor 40, arranged on the coupling sleeve 24. It is also possible to arrange the rotor 40 directly on the output shaft 20. The pump device 22 also comprises a stator 42 interacting with the rotor 40 and being arranged in the house 18 so as not to be rotatable. Preferably, the pump device 22 is adapted as a crescent pump, which entails that it comprises a companion flange 44, operated by the rotor 40. The rotor 40 comprises peripherally arranged teeth 46, which are oriented radially outwards and which, when the rotor 40 rotates, interact with radially inwards oriented teeth 48 of the companion flange 44. The stator 42 has an opening 52, eccentric in relation to the central shaft 50 of the rotor 40, which contains the companion flange 44. Thus the companion flange 44 will rotate eccentrically around the rotor 40, creating a pumping effect when the teeth of the rotor 40 and the companion flange 44 interact with each other. The eccentric placement of the companion flange 44 also forms the pump device's 22 fluid inlet 32 and fluid outlet 34. The pump device 22 also comprises an axially shiftable and reconfigurable switching element 54, which in a first state interacts with the rotor 40 and the stator 42, so that substantially no fluid flow is generated by the pump device 22, and in a second state abuts against the stator 42 and the rotor 40, so that a fluid flow is generated through the pump device 22. Preferably, the switching element 54 is a disc spring, which in the first state takes on a cupped shape, and in the second state takes on a substantially plane shape. Figure 2 shows how the switching element 54 is placed in the first state, when no fluid flow or fluid pressure will be built up by the pump device 22. The reason why no flow and pressure are built up in the first state is, that the interacting teeth 46, 48 of the rotor 40 and the companion flange 44 are not able to create a defined volume, when the side of the pump device 22 facing the switching element 54 is open. The interacting teeth 46, 48 of the rotor 40 and the companion flange 44 will therefore move in the volume of transmission oil existing at the pump device 22, without generating a flow or pressure through the fluid outlet 34. Thus, no power is required in the form of pumping by the pump device 22, which in turn entails that very little transmitted power is required from the output shaft 20. This results in reduced fuel consumption for the vehicle 1 when no take-off module 14 is mounted on the PTO 16. The house 18 comprises axially oriented bores 56, forming channels for a flow of fluid both to and from the take-off module 14, which is designed to be connected to the PTO 16. Bores 56 are also designed to receive a control element 58 (see Fig. 5) for the switching element 54, as explained in more detail below. The bores 56 are connected to tracks 60, formed in the house 18.

Fig. 3 shows a plane view of the PTO 16. It is apparent how several bores 56 are arranged in the circumferential direction of the house 18. The figure shows four bores 56, but fewer or more than four bores 56 may be arranged in the house 18. Preferably, the end turned away from the gearbox 6 of the house 18 (Fig. 2) is provided with an attachment flange (not shown) to attach the take-off module 14 (Fig. 1 ).

Fig. 4 shows a cross-sectional view along the line I - I in Fig. 2. It is apparent that the pump device 22 comprises a rotor 40, a stator 42 and a companion flange 44, and that the pump device 22 is built as a crescent pump. In this context, it should be men- tioned that the pump device 22 could comprise another type of pump, e.g. a gerotor or a cogwheel pump.

Fig. 5 pertains to a cross-sectional view of the PTO 16 with a connected take-off module 14. The take-off module 14 comprises a coupling shaft 66, which is connected to the coupling sleeve 24 with splines 30. The take-off module 14 comprises a control element 58 for the switching element 54. The control means 58 preferably consists of a spigot 58, extending substantially in parallel with the take-off module's 14 coupling shaft. When the take-off module 14 is mounted on the PTO 16, one or several spigots 58 are inserted in the bores 56. The spigots 58 will then come into contact with, and axially shift, a ring 62, which abuts against the disc spring 54. The ring 62 has such a shape that it partly extends into the tracks 60 inside the house 18, which tracks 60 interact with the bores 56. When the ring 62 is shifted axially, the disc spring 54 will be pressed against the pump device's 22 side and be deformed, so that the disc spring 54 takes on a substantially plane shape. The disc spring 54 is thus moved into the second state by overcoming the spring force of the disc spring 54. Thus, the disc spring 54 will abut in a sealing manner against one side of the pump device 22, entailing that a flow and pressure of the transmission oil may be formed. Transmission oil is then sucked up from the gearbox 6 by the pump device 22, through the hose or the conduit 36, and further through the pump device's fluid inlet 32. Subsequently, the transmission oil is pressed out through the fluid outlet 34 of the pump device 22 and moved along further between an opening formed between the disc spring 54 and the coupling sleeve 24, and an opening formed between the ring and the coupling sleeve 24. Finally, the transmission oil is moved further along, to the tracks 60 and the bores 56 in the house 18 and in the take-off module 14. The transmission oil's flow route is indicated by arrows p in Fig. 5. The ring 62 and the lid 39 are held in place by a respective circlip 64, so that the lid 39 is fixed in an axial direction and the axial shift of the ring 62 is limited. The pump device's 22 construction, as well as the interaction of the circlips 64, the ring 62 and the lid 39 with the pump device 22, makes it very easy to mount in the house 18 and also easy to dismantle in case of maintenance or replacement.

The components and features specified above may within the framework of the invention be combined between different embodiments specified.