Power transmission system and lubrication arrangement

Abstract

The invention relates to a power transmission system (11) which includes a rotary articulated- joint shaft (12), which articulated- joint shaft (12) in turn includes a shaft (14) having two ends (16, 18), articulated joints (20,22) respectively arranged at each end (16, 18), bearing units (24,26), lubrication channels (30) for supplying lubricant to the bearing units (24,26), and a lubrication system (10) is arranged in the shaft (14), wherein the lubrication system includes a lubricant chamber (32), a flow channel (34) for conducting lubricant to the bearing units (24,26), a valve unit (36) connected to the flow channel (34) or to the lubricant chamber (32) for turning the flow of lubricant on and off, an electric actuator (42) for operating the valve unit (36), wherein the electric actuator (42) is configured to turn on the flow of lubricant from the lubricant chamber (32) to the flow channel (34) by means of the valve unit (36) only when the shaft (14) is rotating at a selected rotational speed, and a self-powered actuating unit (40) for producing a force for forcing lubricant out of the lubricant chamber (32), wherein at least the lubricant chamber (32), the valve unit (36), the electric actuator (42) and the actuating unit (40) are arranged essentially coaxially to the longitudinal axis of the shaft (14) inside the shaft (14). The invention also relates to a lubrication arrangement.

Description

[0001] POWER TRANSMISSION SYSTEM AND LUBRICATION ARRANGEMENT

[0002] The invention relates to a power transmission system which includes a rotary articulated- joint shaft, which in turn includes a shaft having two ends,

[0003] - articulated joints respectively arranged at each end,

[0004] - respective bearing units for supporting the articulated joints, lubrication channels for supplying lubricant to the bearing units, and a lubrication system arranged in the shaft, wherein the lubrication system includes

[0005] - a lubricant chamber for storing lubricant,

[0006] - a flow channel connected to the lubricant chamber and configured to conduct lubricant from the lubricant chamber to the bearing units, a valve unit connected to the flow channel or to the lubricant chamber for turning the flow of lubricant on and off,

[0007] - a self-powered actuating unit for producing a force for forcing lubricant out of the lubricant chamber, and

[0008] - an electric actuator for operating the valve unit, wherein the electric actuator is configured to turn on the flow of lubricant from the lubricant chamber to the flow channel by means of the valve unit.

[0009] The invention also relates to a lubrication arrangement.

[0010] Various types of rotary articulated- joint shafts are known from a wide range of applications as part of a power transmission in which there is a difference in angle between the power output shaft and the power input shaft of two rotating objects. The most common applications are, for example, the articulated- joint shafts in vehicle power transmissions known as Cardan shafts, the articulated- joint shafts between the power-take- off (PTO) shaft of a tractor and an implement, or industrial articulated- joint shafts between motors that rotate, for example, rolls or the like and an object of application, for example rolls in the paper or pulp industry and their drive motors, which have a rotary articulated- joint shaft between them .

[0011] Common to all the articulated- joint shafts mentioned in the foregoing is that they have a fixed or telescopic shaft part, consisting of one or more parts, and articulated joints with bearing units arranged at both ends. As rotating components, the bearing units require periodic lubrication to reduce friction between the moving parts. Depending on the object of application, lubrication can be quite difficult to carry out as a maintenance operation, as the objects of application can be dirty, hot or confined. In addition, for example, lubrication can only be carried out in many applications when the articulated- joint shaft is stationary, so that clearances are negligible at certain points of the bearing unit and the ability of the lubricant to reach all lubrication points can be limited or even blocked. The right dosing of the lubricant can also be challenging, and tools used for lubrication such as a lubricant gun, if used carelessly, can ruin the sealing of the bearing unit.

[0012] The publication DE 202018103844 U, which discloses an articulated- joint shaft 12 with a lubrication of the bearing units of the articulated joitns by means of a lubrication chamber and a lubrication system arranged in the shaft, is known from the prior art. The lubrication system continuously supplies lubricant for the lubrication of the bearing units. A problem here, however, is that a continuous lubrication consumes a considerable amount of lubricant, which increases the need for a frequent replenishment of the lubricant. A further problem with this lubrication system is that it is structurally complex and costly to implement, as it includes a generator powered by the rotation of the articulated- joint shaft and a dosing unit powered by the generator, which is responsible for dosing the lubricant.

[0013] An object of the invention is to provide a power transmission system that is simpler and that requires less maintenance than the solutions of the prior art. The characteristic features of a power transmission system according to the invention are set out in the attached patent claim 1. A further object of the invention is to provide a lubrication arrangement that is more reliable than the lubrication arrangements of the prior art. The characteristic features of a lubrication arrangement according to the invention are set out in the attached patent claim 12.

[0014] The object of a power transmission system according to the invention is achieved by a power transmission system which includes a rotary articulated- joint shaft, which in turn includes a shaft having two ends, articulated joints respectively arranged at each end, respective bearing units for supporting the articulated joints, lubrication channels for supplying lubricant to the bearing units, and a lubrication system arranged in the shaft. The lubrication system includes a lubricant chamber for storing lubricant, a flow channel connected to the lubricant chamber and configured to be connected to the lubrication channel for conducting lubricant from the lubricant chamber to the bearing units, a valve unit connected to the flow channel or to the lubricant chamber for turning the flow of lubricant on and off, and an electric actuator for operating the valve unit. The lubrication system further includes a self-powered actuating unit for producing a force for forcing lubricant out of the lubricant chamber, and said electric actuator is configured to turn on the flow of lubricant from the lubricant chamber to the flow channel by means of the valve unit. At least the lubricant chamber, the valve unit, the actuator and the actuating unit are arranged essentially coaxially to the longitudinal axis of the shaft inside the shaft.

[0015] In the power transmission system according to the invention, the self-powered actuating unit makes it possible to implement a supply of lubricant from the lubricant chamber to the bearing units simply and reliably by means of positive pressure and without separate pumps or dosing devices, which would consume energy and require control. Moreover, when implemented by this actuating unit, the supply pressure of the lubricant is constantly at a suitable level, and the seals of the bearing unit are not ruined by an excessive pressure during lubrication. By arranging the lubricant chamber, the actuating unit, the actuator and the valve unit coaxially to the longitudinal axis of the articulated- joint shaft inside the articulated- joint shaft, it is possible to ensure that the articulated- joint shaft remains balanced, as the centre of mass of the parts of the lubrication system is on the centre line of the shaft. This facilitates the implementation of the lubrication system as a single cylindrical structure that is easy to arrange at the centre of the articulated- joint shaft.

[0016] In this context, the term "essentially coaxial" means that a maximum deviation of the position of the lubricant chamber, the valve unit, the actuator and the actuating unit from the centre line in a transverse direction is 20 mm, preferably 10 mm. The centres of mass of the components are thus very close to the centre line of the articulated- joint shaft and an imbalance caused by the same is very small and can be taken into account by balancing out the components of the lubrication system with respect to each other in relation to the centre line .

[0017] Preferably, the lubrication system is arranged in the shaft in such a manner that the centre of mass of the lubrication system is on the centre line of the shaft.

[0018] Preferably, the same lubrication system can be configured to provide lubrication for the bearing units at both ends of the articulated- joint shaft. Alternatively, a separate lubrication system can be used in connection with the bearing units at each end, although this doubles the number of necessary components and the work involved in replenishing the lubricant.

[0019] In this context, the term "articulated- joint shaft" is to be understood in a broad sense as including all types of power transmission shafts that are equipped with two articulated joints and that contain a lubrication system for the lubrication of the bearing units of the articulated joints.

[0020] Preferably, the articulated joint is a universal joint . The universal joint is the most common type of joint in an articulated- joint shaft.

[0021] Preferably, the actuating unit includes a sealed pressure accumulator for producing a driving force, a pressure-reducing valve for reducing the pressure of the pressure accumulator, a working cylinder for the reduced pressure of the pressure accumulator, and a piston for pushing the lubricant through the action of the pressure of the working cylinder. Such a structure can be arranged coaxially in series and makes it possible to fill the lubricant chamber without disassembling the articulated- joint shaft and using the same lubrication channels that are used for the lubrication of the bearing units .

[0022] By means of the self-powered actuating unit, the pressure level in the pressurized lubricant chamber decreases as the amount of lubricant in the lubricant chamber decreases. The pressure of the lubricant chamber must thus be very high when the lubricant chamber is full so that there is also a sufficient pressure to supply the lubricant when the lubricant chamber is nearly empty. The pressure initially generated by the actuating unit is thus too high and must be reduced by the pressure- reducing means so that the supply pressure of the lubricant can always be kept constant and at a suitable level.

[0023] According to one embodiment, the lubrication system includes a cylindrical body inside which the lubricant chamber, the working cylinder and the piston are arranged, wherein the piston separates the working cylinder and the lubricant chamber from each other, wherein the piston is freely movable inside the cylindrical body according to the action of the pressure in the lubricant chamber and in the working cylinder. The piston can thus be used for two distinct purposes, namely for pushing lubricant out of the lubricant chamber for the lubrication of the bearing units and, when the lubricant chamber is refilled, for repressuri zing the medium of the pressure accumulator.

[0024] Preferably, the lubricant chamber, the valve unit and the actuating unit are configured to be connected in series in the form of threaded connections. This enables a small space requirement in the transverse direction of the articulated- joint shaft and an easy connectability of the components. Preferably, the end of the lubrication channel on the side of the bearing unit can be disconnected from the bearing unit and used to fill the lubricant chamber and to repressurize the pressure accumulator when the articulated- joint shaft is stationary. The lubricant chamber and the pressure accumulator can thus both be filled using the same lubrication channel by means of a lubricant gun.

[0025] Preferably, with respect to the operating pressure levels and volumes of the pressure accumulator and of the working cylinder, the actuating unit is configured in such a manner that the limit value resulting from the product of pressure and volume does not exceed 50 bar*L, and the largest dimension of the pressure accumulator and of the working cylinder does not exceed 152 mm. The thus implemented actuating unit and, as a result, the entire lubrication system can be implemented in such a manner that it does not count as pressure equipment subject to the EU' s Pressure Equipment Directive 2014 / 68 / EU or to the equivalent North American ASME standard, but rather less stringent requirements according to good engineering practice can apply. As a result, it is possible to obtain an overall design that is more economical in terms of its cost of investment than pressure equipment.

[0026] Preferably, the medium used in the pressure accumulator is nitrogen gas .

[0027] Preferably, the articulated- oint shaft includes a space for the lubrication system, wherein said space is formed coaxially to the axis of rotation of the articulated- joint shaft. In other words, the space is an integrated part of the articulated- joint shaft. This space can formed together with the articulated- joint shaft, or it can be formed as a separate tube to be welded coaxially in a hollow articulated- joint shaft or as a coaxial bored hole in a solid shaft.

[0028] Alternatively, the actuating unit can be a solution implemented by means of, for example, a spring, a combination of a spring and a pneumatic cartridge, a supercapacitor, a solenoid, a worm screw, a servomotor or electricity.

[0029] According to a preferred embodiment, the lubrication system includes a sensor for sensing a rotation of the shaft, wherein the sensor is configured to control the electric actuator to perform a lubrication only when the shaft is rotating. Practical tests have shown that gravity-based actuators, for example, are both difficult to implement and difficult to set. In contrast, an electric actuator can be set much more easily and its operation can also be controlled remotely. As the lubrication of the bearing units of the articulated- joint shaft is only enabled by the actuating unit when the articulated- joint shaft is rotating, there is less consumption of lubricant while lubrication only occurs when the lubricant can contact each object to be lubricated and lubrication is reliable.

[0030] Preferably, the sensor used is an angular position sensor. With an angular position sensor, it is possible to determine reliably and simply when the articulated- joint shaft is rotating and lubrication can be carried out.

[0031] According to a preferred embodiment, the electric actuator includes an electric motor and a transmission connected thereto, which are configured to operate a valve stem belonging to the valve unit in order to open and close the flow channel. By means of the electric motor and the transmission, it is possible to implement a compact actuator that produces a sufficiently large force at a sufficient speed to control the valve unit. The torque produced by the combination of the electric motor and the transmission can be up to 600 times greater than that of a solenoid motor.

[0032] Preferably, the electric motor is arranged in the longitudinal direction of the articulated- joint shaft. Its space requirements in the transverse direction of the articulated- joint shaft are thereby very small.

[0033] According to another embodiment, the electric actuator is a solenoid motor that includes a return spring for returning the shaft belonging to the solenoid motor in order to close the flow channel by means of the valve unit when the solenoid motor is de-energized . A solenoid motor is a simple component which can be implemented in a very small size class and which can consequently readily fit inside the shaft as part of the rotating mass. On the other hand, the power output of a solenoid motor is significantly lower than that of an electric motor, so that it may be difficult to produce a sufficiently large force with the same to operate the valve unit against the return spring, which for its part can reliably close the lubricant chamber when the solenoid is not in operation.

[0034] Preferably, the lubrication system includes a self-powered power source, preferably a battery or rechargeable battery, for producing the power for operating the actuator. The lubrication system can thus be implemented without power being provided from outside the system, which facilitates implementation .

[0035] Preferably, the power source includes a power-supply connection for charging the power source. The power source can thus be a fixed part of the lubrication system and does not need to be removed or replaced. Preferably, the lubrication system further includes a circuit unit for controlling the electric actuator.

[0036] Preferably, in a power transmission arrangement according to the invention, the lubricant chamber is an integrated part of the lubrication system and does not need to be removed and replaced .

[0037] Preferably, the lubrication system is integrated inside the articulated- joint shaft and is not an extension of the same, which would necessitate separate force-transmitting interfaces .

[0038] The object of a lubrication arrangement according to the invention is achieved by a lubrication arrangement which includes a power transmission system according to any one of the embodiments of the invention described in the foregoing and a lubricant supply means for supplying lubricant to a lubricant chamber of the power transmission system, wherein the lubricant supply means includes a pressure relief valve for reducing the pressure of the supplied lubricant to a selected level.

[0039] With the lubrication arrangement according to the invention, the lubrication system of the power transmission system can be replenished with lubricant mainly using commonly used tools suitable for lubrication, such as a conventional lubricant gun. The pressure relief valve makes it possible to protect components of the lubrication system of the power transmission system according to the invention from an excessive pressure of the supply means, which could damage the components. In the lubrication arrangement according to the invention, the filling of the lubricant chamber and the re-pressurization of the actuating unit preferably occur simultaneously, which reduces the number of operations that a lubrication involves.

[0040] Preferably, the lubricant supply means is a lubricant gun. A lubricant gun, or grease gun, is already virtually mandatory equipment for all applications of an articulated- joint shaft, so that a new lubricant supply means is not needed.

[0041] Preferably, the lubrication arrangement includes an external user interface for controlling the lubrication system, and the circuit unit includes wireless communication means for transmitting data between the circuit unit and said external user interface, wherein the communication means are preferably communication means that utilize a personal area network (PAN) , most preferably communication means utili zing Bluetooth®. This enables the transmission of data from the lubrication system to the external user interface as well as a control from the external user interface to the circuit board.

[0042] Preferably, the PAN communication devices are bidirectional, so that data can be transmitted to and from the circuit board. This enables an efficient data transfer and lubrication control .

[0043] The circuit unit can also be configured to send data regarding the opening state of the valve unit via the wireless communication means to an external user interface in order to monitor the amount of lubricant in the lubricant chamber. Information, for example regarding the amount of lubricant in the lubricant chamber or the time of delivery of the lubricant, can thus be transmitted to a separate operating system for the management of the lubrication. A user can thus check how long the lubricant chamber has been in use and when it needs to be replaced, for example, on the user interface of a phone using an app .

[0044] The circuit unit can be configured to receive data for controlling the opening state of the valve unit via said wireless communication means from an external user interface in order to regulate the lubrication. This makes it possible to control the lubrication from an external interface, which can be, for example, an Android®- or iOS®-based application that the user can control from their smartphone.

[0045] Preferably, the articulated- joint shaft is an articulated- joint shaft of a tractor. The maintenance of articulated- joint shafts of tractors under working conditions is particularly challenging because of the dirty conditions.

[0046] Alternatively, the articulated- joint shaft is a Cardan shaft of a vehicle.

[0047] Alternatively, the articulated- joint shaft is an articulated- joint shaft between a roll and a drive motor of a fiber web machine .

[0048] The invention, which is not limited to the embodiments described in the following, is explained in more detail with reference to the attached figures, wherein

[0049] Figure 1a shows an application of a power transmission system according to the invention in connection with an articulated- joint shaft of a tractor,

[0050] Figure 1b shows an application of a power transmission system according to the invention in connection with a Cardan shaft of a vehicle,

[0051] Figure 1c shows an application of a power transmission system according to the invention in connection with an industrial articulated- joint shaft,

[0052] Figure 2a shows an implementation of an actuator according to a first embodiment in the power transmission system with the valve unit in an open position,

[0053] Figure 2b shows an implementation of an actuator according to the first embodiment in the power transmission system with the valve unit in a closed position,

[0054] Figure 3a shows a preferred embodiment of the power transmission system in an operating mode in cross section,

[0055] Figure 3b shows a preferred embodiment of the power transmission system in a filling mode in cross section,

[0056] Figure 4a shows the lubrication system of the power transmission system of Figure 3a on its own in a side view,

[0057] Figure 4b shows the cross section A-A indicated in Figure 4a,

[0058] Figure 4c shows the cross section C-C indicated in Figure 4a,

[0059] Figure 5a shows the combination of the actuator and the valve unit in a side view,

[0060] Figure 5b shows the structure shown in Figure 5a axonometrically ,

[0061] Figure 5c shows the structure shown in Figure 5a in an end view, Figure 5d shows the section D-D indicated in

[0062] Figure 5c.

[0063] The power transmission system 11 according to the invention includes, as shown in Figures 3a and 3b, an articulated- joint shaft 12, which in turn further includes a shaft 14 having ends 16 and 18, articulated joints 20 and 22 connected to the ends 16 and 18, and their bearing units 24 and 26. The shaft 14 additionally includes lubrication channels 30 for delivering lubricant to the bearing units 24 and 26 and a lubrication system 10 for implementing the lubrication. Although an articulated- joint shaft implemented solely by means of a one- piece solid shaft is shown in embodiments of the figures, it is understood that the shaft of the articulated- joint shaft can also be a shaft that consists of two parts, for example with a telescopic structure, as shown in Figures 3a and 3b.

[0064] In Figure la, the articulated- joint shaft 12 of the power transmission system according to the invention is arranged between a tractor 100 and an implement 102 in order to transmit power from the power output shaft of the tractor to the power input shaft of the implement. This is a particularly advantageous application of the power transmission system according to the invention, because the lubrication of articulated- joint shafts of tractors is carried out under variable and often challenging conditions in which there is a clear need to simplify and standardize lubrication operations. Moreover, it can be necessary to take apart the articulated- joint shaft and / or its protective elements in order to carry out the greasing. This is a time-consuming and difficult operation to carry out, because articulated- joint shafts can be very heavy and dirty. It has been reported that an interruption due to the greasing of an articulated- joint shaft can last up to 8 hours. The articulated- joint shaft of the power transmission system according to the invention can also be part of the power transmission of a vehicle, as shown in Figure lb. In other words, it can replace the structure known as a Cardan shaft. The articulated- joint shaft is constantly subject to the effects of weather conditions in this embodiment too, and it can be necessary to carry out the lubrication of the articulated- joint shaft under demanding conditions when the articulated- joint shaft is very dirty.

[0065] The articulated- joint shaft of the power transmission system according to the invention can be implemented as part of an industrial power transmission as shown in Figure 1c, more specifically, for example, between a roll and a drive motor of a machine for processing a fibre web. In these types of applications, the design of the articulated- joint shaft is freer inasmuch as the weight of the articulated- joint shaft is not a critical factor. On the other hand, the articulated- joint shaft is often very heavy, which places a heavy load on the bearing units, which increases the importance of lubrication. Although the operating position of a roll in a machine for processing a fibre web is constant, it is necessary to use an articulated- joint shaft between the drive motor and the roll because the roll can be subjected to bending moments, so that a change in angle is absorbed by the articulated joint of the articulated- joint shaft.

[0066] Figures 2a and 2b show a first embodiment of a lubrication system of a power transmission according to the invention, while Figures 3a and 3b show a second embodiment. In both embodiments, the lubrication system arranged in the shaft 14 of the articulated- joint shaft 12 includes a lubricant chamber 32 for storing lubricant and a flow channel 34 connected to the lubricant chamber 32 and configured to conduct lubricant from the lubricant chamber 32 to the bearing units, for example as shown in Figure 3a. In addition, the lubrication system 10 includes a valve unit 36 connected to the flow channel 34 or to the lubricant chamber 32 for turning the flow of lubricant from the lubricant chamber 32 on and off according to a selected criterion. Preferably, this criterion is the rotation of the articulated- joint shaft, so that the valve unit 36 only lets lubricant pass from the lubricant chamber 32 to the bearing units when the articulated- joint shaft 12 is rotating; otherwise, the valve unit 36 closes the flow channel 34 or the lubricant chamber 32. The lubricant system further includes an electric actuator 42 for operating the valve unit 36 in such a manner the electric actuator 42 is configured to turn on the flow of lubricant from the lubricant chamber 32 to the flow channel 34 by means of the valve unit 36 only when the shaft 14 is rotating at a selected rotational speed, as well as a self-powered actuating unit 40 for providing a force in connection with the lubricant chamber 32 to force lubricant out of the lubricant chamber 32.

[0067] A difference between the first and the second embodiment is the structure of the electric actuator 42. In the first embodiment shown in Figures 3a and 3b, the electric actuator 42 is a solenoid motor 43, whereas in the second preferred embodiment shown in Figures 3a - 5d, the electric actuator 42 is a combination of an electric motor 112 and a transmission 100.

[0068] The implementation according to the first embodiment and the structure of the electric actuator 42 will now be examined in greater detail with reference to Figures 2a and 2b. The electric actuator 42 is preferably a solenoid motor 43, which is preferably powered by a self-powered power source 68. The self-powered power source 68 can be, for example, a battery or rechargeable battery. The solenoid motor 43 is attached by its shaft 47 to a valve stem 52 belonging to the valve unit 36. The operation of the solenoid motor 43 is controlled by means of the circuit unit 44 preferably using a sensor 46. Preferably, the sensor is an angle sensor. The angular-position sensor 46 continuously monitors the angle of the articulated- joint shaft and determines whether the articulated- joint shaft is rotating or whether it is stationary. If the articulated- joint shaft is rotating, the circuit unit 44 turns on, for example by means of a relay, the power from the power source 68 to the solenoid motor 43, which pulls back the shaft 47 and the valve stem 52 connected thereto, so that the valve unit 36 opens the flow channel 34 and the flow from the lubricant chamber to the lubrication channel 30 as shown in Figure 2a.

[0069] The solenoid motor 43 preferably works against the return spring 45 and, when the solenoid motor 43 is de-energized, the return spring 45 presses the valve stem 52 of the valve unit 36 back into the closed position as shown in Figure 2b. The return spring 45 is preferably dimensioned in such a manner that the force it produces is greater than a counterforce exerted on the valve stem by the lubricant coming through the flow channel .

[0070] Preferably, in addition to the data obtainable from the sensor 46, the circuit unit 44 includes wireless communication means 49 for transmitting data between the circuit unit 44 and an external user interface 70. The communication means are preferably communication means that utilize a personal area network (PAN) , most preferably communication means utilizing Bluetooth®. An advantage of PAN communication means is that they are used very widely, for example in connection with wireless mobile devices, and the programming they involve is simpler than other communication means.

[0071] By means of the wireless communication means 49, it is possible to provide the circuit unit 44 with a second, additional criterion for turning on the lubrication, which can be a specific timing in addition to the rotation of the articulated- joint shaft, for example a lubrication for 10 minutes every 6 - 8 hours. If necessary, the timing of the lubrication can also be changed via an external user interface. Lubrication is thus only carried out when these two criteria are met, wherein preferably a logic unit belonging to the circuit unit monitors the fulfilment of the criteria. Moreover, the circuit unit can also be configured to collect data on, for example, the use of the actuator, a voltage level of the power source, a pressure level of the lubricant chamber, a monitoring of the condition of the bearing units, for example by monitoring a voltage level, or other similar information, and to store the data in a separate memory. The circuit unit can further be configured to send data via the communication means to an external user interface 70 in order to track maintenance. The external user interface can be, for example, a Windows-, Android- or iOS- based application that a user can access via their end device, or alternatively a control device for controlling the operating environment of the articulated- joint shaft, such as a control unit of a tractor or the like.

[0072] In addition to or instead of an angular position sensor, data regarding the rotation of the articulated- joint shaft can also be provided via the wireless communication means, for example from an external user interface.

[0073] Preferably the pressure-reducing means 56 shown in Figures 2a and 2b are used in connection with the self-powered actuating unit. The pressure-reducing means can be, for example, a pressure regulator that reduces the pressure to a desired constant level in all operating conditions. For example, when a pressure accumulator is used as the self-powered actuating unit, the higher pressure level of the new pressure accumulator can be made to correspond to a desired pressure level throughout lubrication, although the pressure of the accumulator decreases as a result of use. For example, the pressure regulator marketed under the brand name "233F" by the German company Aircom GmbH can be used as the pressure regulator .

[0074] Figures 3a - 5d show a preferred embodiment of the power transmission system in which the lubricant chamber 32 is fillable. The second preferred embodiment of the electric actuator 42, in which the electric actuator is a combination of an electric motor and a transmission, is used in this embodiment. The lubrication system in this embodiment includes a nitrogen-filling valve 81, a pressure accumulator 82, a pressure-reducing valve 83 with a check valve as the pressure- reducing means, a working cylinder 84 and a piston 85, which together form the self-powered actuating unit 40. In addition, the lubrication system 10 includes a valve unit 36, a circuit board 87, a battery as the power source 68, a lubrication channel for lubricant which leads to the articulated joint 30 and which is also used to fill the lubricant chamber, and a charging connector 90.

[0075] Figure 3b also shows a lubrication arrangement according to the invention, which also includes, in addition to the power transmission system according to the invention, supply means for supplying lubricant, which in this case is a lubricant gun 92, and a pressure relief valve 93 of the supply means. Preferably, the lubrication arrangement additionally includes an external power source 91 for charging the power source 68 of the lubrication system.

[0076] The operation of the embodiment shown in Figures 3a - 5d will now be described in more detail. Nitrogen is charged into the pressure accumulator 82 via the nitrogen valve 81 in order to provide a pressure sufficient for lubrication. In this context, it is understood that the pressure employed on the side of the pressure accumulator 82 must be of a magnitude to enable a sufficient lubrication pressure throughout lubrication. In other words, the pressure in the pressure accumulator 82 decreases over a lubrication operation and must also be of a sufficient magnitude at the very end of the lubrication operation before the lubricant chamber is refilled. The pressure of the pressure accumulator 82 is reduced by means of a pressure-reducing valve 83 to a pressure sufficient for the piston 85 of the working cylinder 84 for lubrication. By means of the pressure-reducing valve 83, the piston 85 moves at a constant pressure over the entire stroke in the working cylinder 84 because there is sufficient nitrogen on the side of the pressure accumulator 82.

[0077] When selecting the pressure of the pressure accumulator and the working cylinder, it is advantageous to design the actuating unit in such a manner that it is interpreted as a device subject to "good engineering practice" to which pressure vessel regulations do not apply. Compliance with pressure vessel regulations requires a structure that is more expensive than that of a device subject to "good engineering practice" and, in addition, the approval of a device subject to pressure vessel regulations is onerous. As a result, with respect to the operating pressure levels and volumes of the pressure accumulator and of the working cylinder, the actuating unit is configured in such a manner that the limit value resulting from the product of pressure and volume does not exceed 50 bar*L, and the largest dimension of the pressure accumulator and of the working cylinder does not exceed 152 mm. For the EU Pressure Equipment Directive 2014 / 68 / EU, it is not the pressure level or volume in isolation that is decisive, but rather their product. For the North American ASME standard, on the other hand, dimension is the key criterion. It is advisable to take both into account when dimensioning the actuating unit.

[0078] According to a preferred embodiment, a sufficient lubrication pressure is achieved by using a starting pressure of 25 bar in the pressure accumulator when the lubricant chamber is full of lubricant, so that the pressure on the side of the working cylinder in the end state is 13 bar when a pressure regulator is used that effects a reduction of 10 bar, a length of the lubricant chamber is 10 cm and a diameter of the piston is 2.22 cm. The level of lubrication of the articulated- joint shaft is generally considered sufficient if a gram of grease is supplied for every eight hours of operation of the articulated- joint shaft .

[0079] Lubricant is pushed by the piston 85 along the lubrication channel 30 to the bearing unit of the articulated- joint shaft. The operation of the valve unit 36 is preferably controlled with a mobile phone via Bluetooth, using the wireless communication means of the circuit board 87 to open and close the valve unit 36 in a manner desired by the user. Preferably, lubrication is regulated by regulating the opening state of the valve unit with an on / off type of control rather than a flow-throttling partial opening. This makes it possible to constantly keep the flow at a sufficiently high level.

[0080] When the piston 85 has reached the end of the valve unit 36, i.e. the end of the lubricant chamber, the lubricant chamber 32 is essentially empty and the lubrication system has lubricated the bearing unit. The lubricant chamber 32 must consequently be refilled with lubricant, preferably using a lubricant gun 92 as the lubricant supply means. Analogously, the self-powered power source 68, i.e. the rechargeable battery or battery, must also be recharged by an external power source 91.

[0081] The filling of the lubricant chamber 32 is preferably carried out using the same lubrication channel 30 through which lubricant is supplied from the lubricant chamber 32 to the bearing unit 24,26. In a filling situation, the end of the lubrication channel 30 is disconnected from the bearing unit 24,26 and connected to the lubricant supply means 92 using the pressure relief valve 93 as a connector.

[0082] The lubricant chamber 32 is refilled with lubricant by first opening the valve unit 36, so that lubricant can be pushed into the lubricant chamber 32 through the lubrication channel 30 using, for example, a pressure of 29.5 bar. This is achieved by using the pressure relief valve 93 in the lubricant gun 92 preferably used as the lubricant supply means, wherein the pressure relief valve 93 lets out a pressure of, for example, more than 50 bar by discharging a part of the lubricant into a separate excess-pressure tank. Proceeding in this manner prevents a breakdown of the valve unit 36, as it is possible with a lubricant gun 92 to obtain a pressure of up to 1000 bar, which the valve unit 36 cannot withstand. The reason why the pressure accumulator requires a higher pressure than the working cylinder is the friction caused by the 0-rings of the piston 85. The filling pressure must therefore be higher than the combined initial pressure of the pressure accumulator 82 and the friction caused by the 0-rings of the piston 85. Filling the lubricant chamber 32 simultaneously causes the piston 85 to move back towards its starting position, whereby it compresses the nitrogen in the working cylinder. The pressure-reducing valve 83 has a check valve which lets pressure pass through it when the pressure on the side of the working cylinder 84 is greater than the pressure in the pressure accumulator 82. The piston 85 can thereby move to its initial position simultaneously with the refilling with new lubricant, and the nitrogen of the pressure accumulator starts to be compressed back into the pressure accumulator 82. When the lubricant chamber 32 is full of lubricant, the pressure accumulator 82 is pressurized at the starting pressure and the lubrication system is ready for a new operation.

[0083] The same lubricant channel is preferably used both to fill the lubricant chamber 32 and to pressurize the pressure accumulator .

[0084] While the lubrication system 10 is being filled with new lubricant, the battery in the lubrication system is charged using an external power source.

[0085] Figures 4c and 5a - 5d show a preferred implementation of a valve unit 36 and an electric actuator 42 integrated into same unit. In this embodiment, the electric actuator 42 is formed by an electric motor 112 and a transmission 100 connected thereto. Connected to the shaft of the transmission 100 is a gearwheel by means of which a second gearwheel 106 is rotated. The second gearwheel 106 is attached to the stem 52 of the valve unit 36, which stem 52 is preferably connected by threads to a combined body 102 of the valve unit 36 and the electric actuator 42. When the valve stem 52 moves in its longitudinal direction, the valve stem 52 opens or closes the flow channel 34 from the lubricant chamber 32. When the flow channel 34 is opened, lubricant can pass into the lubrication channel 30 and through it to the bearing unit.

[0086] The electric motor 112 is preferably arranged in the body 102 in the longitudinal direction of the articulated- joint shaft, so that it takes up very little space. The electric motor can be, for example, a Micro Metal Gearmotor miniature electric motor with a diameter of 10 - 12 mm, which can produce a torque of 0.7 Nm and which enables an opening of the valve stem within a second. By means of the transmission 100, which is connected as an extension of the electric motor, it is possible to change the gear ratio, which is preferably between 1 / 1000 and 1 / 400.

[0087] As shown in Figures 3a - 4b, the lubrication system 10 of the power transmission arrangement according to the invention is preferably formed coaxially to the axis of rotation of the articulated- oint shaft 12, along the centre line of the articulated- joint shaft 12 inside the articulated- joint shaft 12. For example, in tractor applications, the articulated- joint shafts are often hollow, so that a tube for the lubrication system can be welded inside the articulated- joint shaft to form a housing for the lubrication system. In heavier applications such as, for example, industrial articulated- joint shafts, which are often solid castings, the space for the lubrication system can be formed by machining a hole along the centre line, in which hole the components of the lubrication system are arranged. Preferably, the lubricant chamber, the actuating unit, the valve unit, the electric actuator, the circuit board and the self-powered power source together form a structure that is about 30 cm long, with a lubricant-chamber volume of 100 ml. This dimensioning provides sufficient lubricant for about a month at a time at a daily operation of the articulated- joint shaft of 8 hours. Although Figures 3a and 3b show the lubrication system 10 with a separate unit at each end 16, 18 of the articulated- joint shaft 12, it is understood that the invention can also be implemented in such a manner that the transmission system includes only one lubrication system connected to two lubrication channels. This makes the maintenance of the lubrication system easier and reduces the cost of investment, but in some cases can cause problems due to a lack of space in the articulated- joint shaft, which can make it difficult to arrange a lubrication line from one end of the articulated- joint shaft to the other.

[0088] The wireless communication means and the sensor that monitors the rotation of the articulated- joint shaft can all be integrated into the circuit board.

[0089] In this context, it is understood that it is also possible to employ the lubrication system, the actuating unit and the combined structure of the valve unit and the actuator described in the present application independently as independent inventions in different application environments.

Claims

CLAIMS1. A power transmission system (11) which includes a rotary articulated- joint shaft (12) , which articulated- joint shaft (12) in turn includes a shaft (14) having two ends (16, 18) , articulated joints (20,22) respectively arranged at each end (16, 18) , respective bearing units (24,26) for supporting the articulated joints (20,22) , lubrication channels (30) for supplying lubricant to the bearing units (24,26) , and a lubrication system (10) arranged in the shaft (14) , wherein the lubrication system includes a lubricant chamber (32) for storing lubricant , a flow channel (34) connected to the lubricant chamber (32) and configured to conduct lubricant from the lubricant chamber (32) to the bearing units (24,26) , a valve unit (36) connected to the flow channel (34) or to the lubricant chamber (32) for turning the flow of lubricant on and off, a self-powered actuating unit (40) for producing a force for forcing lubricant out of the lubricant chamber (32) , and an electric actuator (42) for operating the valve unit (36) , wherein the electric actuator (42) is configured to turn on the flow of lubricant from the lubricant chamber (32) to the flow channel (34) by means of the valve unit (36) , characterized in that at least the lubricant chamber (32) , the valve unit (36) , the electric actuator (42) and the actuatingunit (40) are arranged essentially coaxially to the longitudinal axis of the shaft (14) inside the shaft (14) .

2. The power transmission system according to claim 1, characterized in that the actuating unit (40) includes a sealed pressure accumulator (82) for producing a driving force, a pressure-reducing valve (83) for reducing the pressure of the pressure accumulator (82) , a working cylinder (84) for the reduced pressure of the pressure accumulator (82) , and a piston (85) for pushing lubricant through the action of the pressure of the working cylinder (84) .

3. The power transmission system according to claim 2, characterized in that the lubricant chamber (32) , the valve unit (36) and the actuating unit (40) are configured to be connected in series in a form of threaded connections.

4. The power transmission system according to claim 2 or 3, characterized in that, with respect to operating pressure levels and volumes of the pressure accumulator (82) and of the working cylinder (84) , the actuating unit (40) is configured in such a manner that a limit value resulting from a product of pressure and volume does not exceed 50 bar*L, and largest dimension of the pressure accumulator (82) and of the working cylinder (84) does not exceed 152 mm.

5. The power transmission system according to any one of claims 1 - 4, characterized in that an end of the lubrication channel (30) on a side of the bearing unit (24, 26) can be disconnected from the bearing unit (24, 26) and used to fill the lubricant chamber (32) and to repressurize the pressure accumulator (82) when the articulated- joint shaft (12) is stationary .

6. The power transmission system according to any one of claims 1 - 5, characterized in that the lubrication system (10) includes a sensor (46) for sensing a rotation of the shaft (14) , wherein the sensor (46) is configured to control the electric actuator (42) to perform a lubrication only when the shaft (14) is rotating.

7. The power transmission system according to claims 1 - 6, characterized in that the lubrication system (10) includes a self-powered power source (68) , preferably a battery or rechargeable battery, for producing the power for operating the electric actuator (42) .

8. The power transmission system according to any one of claims 1 - 7, characterized in that the lubrication system (10) further includes a circuit unit (44) for controlling the electric actuator (42) .

9. The power transmission system according to any one of claims 1 - 8, characterized in that the electric actuator (42) includes an electric motor (112) and a transmission (100) connected thereto, which are configured to operate a valve stem (52) belonging the valve unit (36) to open and close the flow channel (34) .

10. The power transmission system according to any one of claims 1 - 9, characterized in that the entire lubrication system (10) is arranged essentially coaxially to a longitudinal axis of the shaft (14) inside the shaft (14) .

11. The power transmission system according to any one of claims 1 - 10, characterized in that the lubricant chamber (32) of the power transmission system (11) is an integrated part of the lubrication system (10) .

12. A lubrication arrangement which includes a power transmission system (11) and a lubricant supply means (98) for supplying lubricant to a lubricant chamber (32) of the power transmission system (11) , characterized in that the power transmission system (11) is a power transmission system (11) according to any one of claims 1 - 11 and the lubricant supply means (98) includes a pressure relief valve (93) for reducing pressure of supplied lubricant to a selected level.

13. The lubrication arrangement of claim 12, characterized in that the lubrication arrangement (11) includes an external user interface (70) for controlling the lubrication system (10) , and the circuit unit (44) includes wireless communication means (49) for transmitting data between the circuit unit (44) and the external user interface (70) , wherein the communication means (49) are preferably communication means that utilize a personal area network.

14. The lubrication arrangement according to claim 12 or 13, characterized in that the circuit unit (44) is configured to send data regarding an opening state of the valve unit (36) via the wireless communication means (49) to an external user interface for monitoring the amount of lubricant in the lubricant chamber.

15. The lubrication arrangement according to any one of claims 12 - 14, characterized in that the circuit unit (44) is configured to receive data for controlling the opening state of the valve unit (36) via the wireless communication means (49) from an external user interface (70) for regulating the lubrication .

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