WO2013034154A1

WO2013034154A1 - A mobile lubrication unit and a method for creating a high-pressure flow of lubrication

Info

Publication number: WO2013034154A1
Application number: PCT/DK2011/000099
Authority: WO
Inventors: Lars Birkkjaer Nielsen
Original assignee: Your Global Solution Aps
Priority date: 2011-09-06
Filing date: 2011-09-06
Publication date: 2013-03-14
Also published as: EP2753860A1

Abstract

A mobile lubrication unit (1) comprising at least one motor (2) driving at least one reciprocating positive displacement pump (3) is disclosed. The reciprocating positive displacement pump (3) comprises a lubrication inlet (4), a piston rod (5) acting on a piston (6), which is fitted inside a corresponding cylinder (7) so that a cylinder chamber (8) is established inside the cylinder (7) in front of the piston (6). The cylinder chamber (8) is also provided with a lubrication outlet (9). The mobile lubrication unit (1) is characterized in that the piston rod (5) and/or the piston (6) comprises at least one conduit (10) for establishing fluid communication between the lubrication inlet (4) and the cylinder chamber (8). Furthermore, a method for creating a high-pressure flow of lubrication is disclosed.

Description

A MOBILE LUBRICATION UNIT AND A METHOD FOR CREATING A HIGH-PRESSURE FLOW

OF LUBRICATION

Field of the invention

The invention relates to mobile lubrication unit according to the preamble of claim 1 and a method for creating a high-pressure flow of lubrication.

Background of the invention

Central lubrication systems are well known in the art in relation to wind turbines and other types of heavy-duty equipment that needs lubrication constantly or in short intervals.

However, in relation to some types of machinery and other equipment regular lubrication is not needed or central lubrication systems are not attractive due to cost, weight, space consumption or other and a need for a simple and mobile lubrications system has emerged.

However, to e.g. lubricate a pitch bearing for a wind turbine blade, high- viscous grease has to be pumped into the bearing at a pressure above 100 bar which requires a very powerful pump with a high capacity. But a powerful high-capacity pump including means for driving the powerful pump will inherently be heavy and thereby difficult to make mobile so that it can fit in places that are hard to access and so that it can be carried by a person to the often remote located equipment that needs lubrication.

From the Danish utility model DK 2009 00197 U3 it is therefore known to provide a lubrication apparatus with a rotary-type pump and a number of reciprocating-type pumps where the rotary-type pump and the reciprocating-type pumps are connected in series so that the viscosity of the grease is lowered through the rotary-type pump before it is pressured out of the reciprocating-type pumps under high pressure. However, this lubrication apparatus is expensive and given its complexity not very durable.

An object of the invention is therefore to provide for a lubrication technique that is durable and cost-efficient.

The invention

The invention provides for a mobile lubrication unit comprising at least one motor driving at least one reciprocating positive displacement pump. The reciprocating positive displacement pump comprises a lubrication inlet, a piston rod acting on a piston, which is fitted inside a corresponding cylinder so that a cylinder chamber is established inside the cylinder in front of the piston. The cylinder chamber is also provided with a lubrication outlet.

The mobile lubrication unit is characterized in that the piston rod and/or the piston comprises at least one conduit for establishing fluid communication between the lubrication inlet and the cylinder chamber. When the piston is forced into the cylinder chamber the lubrication is forced out of the cylinder chamber at a pressure up to or even above 250 bar so care has to be taken to ensure that the lubrication is not forced back out through the lubrication inlet. This could be ensured by means of a one-way valve but a valve which can stand such high pressures without at the same time substantially hindering the lubrication from entering is both costly and vulnerable.

If the inlet was provided at the top of the cylinder chamber so that the inlet was only exposed when the piston was in its top position the piston and/or the piston rod would block the inlet when it has moved down a bit. However, the distance between the inlet and the top of the cylinder chamber (i.e. the front of the piston) would at least for some part of the pistons travel be so short that lubrication would be forced back towards and out through the inlet if the piston was not provided with some kind of a seal. But such a seal would constantly have to pass the edge of the inlet which quickly will wear the seal and the seal would be located in the "heart" of the pump making it difficult to replace.

However, by providing the piston rod and/or the piston with a passage through which the lubrication can be fed to the cylinder chamber, it is possible to move the lubrication inlet away from the top of the cylinder chamber (i.e. the front of the piston), thus enabling that the drop of pressure between the cylinder chamber and the lubrication inlet is so high that substantially no or only very small amounts of lubrication is forced out of the inlet even if the inlet is not provided with a one way valve and even if the piston is not provided with a seal. By the term "reciprocating positive displacement pump" is to be understood any kind of pump causing a fluid to move by use one or more oscillating pistons, plungers or membranes. The term does not include rotary pumps where the fluid is moved by the principles of rotation. In an aspect of the invention said piston rod and said piston are formed integrally as one monolithic component.

Forming the piston rod and the piston as one piece is advantageous in that it reduces the number of components in the lubrication unit, it reduces production costs and it provides for a simple pump design.

In an aspect of the invention said at least one conduit is formed as an axial bore in said piston rod and/or said piston, said axial bore being in fluid communication with one or more radial bores. Establishing the fluid communication by means of an axial bore connected to one or more radial bores in the piston rod and/or in the piston is advantageous in that the lubrication inlet can be moved relatively far away from the cylinder chamber and the access between the two is almost none-exciting after the piston has moved the radial bores past the lubrication inlet, whereby ensuring a high pressure drop between the lubrication inlet and the cylinder chamber without the use of one-way valves or dedicated seals, which provides for a simple, efficient and inexpensive pump.

In an aspect of the invention said at least one conduit is formed as one or more channels in the outer surface of said piston rod and/or said piston.

Channels in the piston surface substantially provide the same effect as the abovementioned axial and radial bores. In an aspect of the invention the outer diameter of said piston rod is equal to the outer diameter of said piston.

Making the piston have the same outer diameter as the piston rod is advantageous in that it provides for a simple pump design and in that it enables easy assembly and dismantling of the piston and piston rod in that the equal diameters enables that the piston can be pulled out of the pump through the same bore as the piston rod.

In an aspect of the invention the outer diameter of said piston rod is substantially equal to the inner diameter of said cylinder.

The closer the outer diameter of the piston rod is to the inner diameter of the cylinder the higher the pressure drop will be between the cylinder chamber and the lubrication inlet and it is therefore advantageous to make these substantially equal i.e. with a very little clearance. In an aspect of the invention said lubrication outlet is connected to a pressure gauge.

If a channel in the equipment to be lubricated was somehow blocked the output pressure from the lubrication unit could rise alarmingly thereby risking damage to the pump or overloading the motor. Thus, it is advantageous to provide the lubrication outlet with a pressure gauge so that the unit can either manually or automatically be switched of if a predetermined upper pressure level is reached.

In an aspect of the invention said lubrication outlet is connected to a volume gauge.

E.g. when lubricating a bearing it is important that enough grease is provided to either refill the bearing or to completely replace the used grease. And to avoid overfilling the bearing and to reduce the use of expensive grease it is also important that the correct amount of grease is delivered. Thus, it is advantageous to provide the lubrication outlet with a volume gauge so that the unit can either manually or automatically be switched of when a predetermined volume of lubrication has been delivered.

In an aspect of the invention said volume gauge comprises a switch arranged for being activated by a movable piston, wherein said movable piston is arranged to be moved by incoming lubrication.

Making the volume gauge comprises a switch which detects a position of a movable piston, makes it easy to calculate the volume passing the volume gauge by multiplying the number of signals from the switch with the given volume delivered per full movement of the piston.

In an aspect of the invention said mobile lubrication unit further comprises a controller comprising means for controlling the operation of said motor. Hereby is achieved an advantageous embodiment of the invention.

In an aspect of the invention said controller comprises means for at least partly controlling the operation of said motor on the basis of input from said pressure gauge and/or said volume gauge.

Controlling the operation of the motor on the basis of input from the pressure gauge and/or the volume gauge is advantageous in that in that it thereby is possible to ensure that the unit is not exposed to damaging overloads and it is possible to ensure that exactly an predetermined amount is delivered - thus, reducing cost.

In an aspect of the invention said controller further comprises an input panel for inputting operational parameters. Providing the controller with an input panel enables that an operator can set a desired operational pressure, a desired maximum pressure, a desired amount or other operational parameters thereby ensure higher efficiency and more diverse use of the lubrication unit. In an aspect of the invention said controller comprises means for at least partly controlling the operation of said motor on the basis of said operational parameters.

Hereby is achieved an advantageous embodiment of the invention. In an aspect of the invention said mobile lubrication unit has a capacity of between 0.05 and 5, preferably between 0.1 and 2 and most preferred between 0.1 and 1 litre/min.

Since the lubrication unit is mobile it has to deliver the desired amount of lubrication very fast at least compared to the capacity of commonly known central lubrication systems and it is therefore advantageous that the desired amount of lubrication is delivered fast so that the mobile lubrication unit can be put to use elsewhere. However, if the lubrication is delivered too fast the pump could become too big and heavy to be handled by one person. Thus, the present capacity ranges presents an advantageous relationship between efficiency and size.

In an aspect of the invention said motor is connected to a camshaft and wherein a cam on said camshaft drives said piston rod at least in one direction. Actuating the piston rod by means of a cam is advantageous in that a cam can enable complex motion patterns according to the peripheral contour of the cam.

In an aspect of the invention said cam acts on said piston through a bearing. Making the cam act on the piston through a bearing is advantageous in that the bearing will reduce the friction thereby reducing power consumption and increasing the life of the unit.

In an aspect of the invention a spring drives said piston at least in one direction.

Making a spring act on the piston in the direction opposite the direction which the cam acts on the piston in is advantageous in that it provides for a simple and inexpensive design ensuring that the piston is positively moved in both directions. In an aspect of the invention said motor is an electric motor.

Hereby is achieved an advantageous embodiment of the invention.

In an aspect of the invention said reciprocating positive displacement pump comprises at least two pistons fitted inside corresponding cylinders. Making the displacement pump comprises at least two individual pistons and cylinders is advantageous in that it provides for a more efficient and fast pump having a more continuous output flow.

In an aspect of the invention said at least two pistons fitted inside said corresponding cylinders are arranged in parallel.

Hereby is achieved an advantageous embodiment of the invention.

The invention further provides for a method for creating a high-pressure flow of lubrication. The method comprises the steps of: forcing a piston in a direction out of a corresponding cylinder so that a vacuum is created in a cylinder chamber in front of the piston inside the cylinder,

subsequently creating a fluid communication between a lubrication inlet and the cylinder chamber so that the vacuum draws a lubrication portion from the lubrication inlet and into the cylinder chamber through a conduit in a piston rod driving the piston and/or a conduit in the piston, and

forcing the piston in a direction into the cylinder so that the lubrication portion is forced out of the cylinder chamber through a lubrication outlet.

Drawing the lubrication portion into the cylinder chamber through a conduit in a piston rod and/or in the piston is advantageous in that it hereby is possible to move the lubrication inlet relatively far away from the cylinder chamber to thereby ensure a high pressure drop between the two and consequently a durable and cost-efficient pumping method. In an aspect of the invention said fluid communication is cut off at the first part of said pistons travel into said cylinder.

Cutting the fluid communication off at the first part of pistons travel is advantageous in that the rest of the travel can thereby be used for generating pressure, hereby enabling a simple and efficient pump design.

In an aspect of the invention said lubrication is a high-viscous grease with a kinematic viscosity between 5 and 22, preferably between 7 and 18 and most preferred between 10 and 16 mm²/s at 40°C.

If the viscosity of the grease is too low it is difficult to make is stay in the right place in the equipment to be lubricated and if the viscosity is too high it is difficult to make the grease reach the right places. Thus, the present viscosity ranges provides for an advantageous relationship between efficiency and usability.

In an aspect of the invention said piston is forced in a direction into said cylinder by means of a rotating camshaft.

In an aspect of the invention said piston is forced in a direction out said cylinder by means of a spring.

In an aspect of the invention the operation of said piston at least partly is driven by a motor. In an aspect of the invention the operation of said motor is controlled by a controller at least partly on the basis of inputs regarding desired lubrication output pressure and/or desired output lubrication volume. In an aspect of the invention the operation of said motor is controlled by a controller at least partly on the basis of inputs regarding actual lubrication output pressure and/or actual output lubrication volume.

In an aspect of the invention said controller will stop the operation of said motor if a measurement of said actual lubrication output pressure exceeds a predetermined maximum lubrication output pressure.

In an aspect of the invention said controller will stop the operation of said motor if a measurement of said actual lubrication output volume exceeds or is equal to a desired output lubrication volume.

Figures

The invention will be described in the following with reference to the figures which fig. 1. illustrates an embodiment of a mobile lubrication unit according to the invention, as seen in perspective, fig. 2 illustrates a first cross section of a reciprocating positive displacement pump according to the invention, as seen from the front, fig. 3 illustrates a cross section of a piston rod with axial and radial bore, as seen from the front, fig. 4 illustrates a cross section of a piston rod with channels in the outer surface, as seen from the front, and fig. 5 a mobile lubrication unit fitted in a suitcase, as seen in perspective.

Detailed description

Fig. 1 illustrates an embodiment of a mobile lubrication unit 1 according to the invention, as seen in perspective.

In this embodiment of the invention the lubrication unit 1 comprises a geared motor 2 driving a camshaft 21 through a flexible coupling 27. In this embodiment the motor 2 is an electrical motor but in another embodiment the camshaft 21 could be driven by a pneumatic motor, a hydraulic motor or another type of motor 2. In another embodiment the motor could be connected to the camshaft 21 directly or through meshing gears, through a belt or a chain or through other torque transferring means.

In this embodiment of the invention the lubrication unit 1 is not provided with its own power source to power the motor 2, the controller 19 and other electrically powered components of the lubrication unit 1. The unit 1 is therefore provided with a socket 28 for connecting the unit 1 to an external power source such as the utility grid.

However, in another embodiment the lubrication unit 1 could instead or also require connection to a pressurised air supply, to a hydraulic circuit or another external power sources.

In another embodiment of the invention the lubrication unit 1 could also be provided with an internal power source such as a battery, a fuel cell, a solar panel or other which at least partly could power one or more of the power consuming components of the unit 1. In this embodiment of the invention the camshaft 21 is provided with two cams 22 in form of to ball bearings 23 arranged eccentric to the rotational axis of the camshaft 21. The number of cams 22 corresponds with the number of pistons 6 in the reciprocating positive displacement pump 3 so the number of cams can of course vary accordingly.

In another embodiment of the invention the cams 22 could be formed other than circular such as oval or curved and cam 22 could be provided with another type of bearing 23 such as a needle bearing, a roller bearing or a plain bearing or the cams 22 could comprise no bearing, thus making the cams 22 act directly on the piston rods 5 or through another component.

In this embodiment the camshaft 21 and the cams 22 are provided to actuate the piston rods 5 of the displacement pump 3 but in another embodiment the piston rods 5 could be actuated differently such as by means of pneumatic, hydraulic or electrical actuators or by any other means capable of applying force to the piston rod 5 at least in one directions i.e. at least forcing the piston rod 5 into the cylinder 7 or out of the cylinder 7. The inner details of the displacement pump 3 will be discussed more thoroughly in relation to fig. 2 but as shown in fig. 1 the displacement pump 3 is in this

embodiment provided with a container socket 29 adapted for fixating a lubrication container (not shown) at least during the operation of the lubrication unit 1. The container socket 29 is in fluid communication with a lubrication inlet 4 of the displacement pump 3. In another embodiment the container socket 29 could be formed differently in that it e.g. could comprise a quick coupling or other means for feeding lubrication into the displacement pump 3.

In this embodiment the displacement pump 3 is also provided with a lubrication outlet 9 which is in fluid communication with a pressure gauge 17 for providing the output pressure of the lubrication. In this embodiment the pressure gauge 17 is a pressure transmitter connected to a controller 19 but in another embodiment the pressure gauge 17 could be some sort of manual device or it could be any other type of sensor suited for measuring the pressure of lubrication.

From the pressure gauge 17 the lubrication continues into a volume gauge 18 which in this embodiment comprises a piston that changes its positions back and forth each time a given lubrication volume enters the volume gauge 18. The volume gauge 18 is further provided with an inductive switch which registers each time the piston has moved back and forth in the volume gauge 18. Thus, by feeding the output of the inductive switch to the controller 19 the output volume can be calculated by multiplying the number of signals with the given lubrication volume inside the volume gauge 18. In another embodiment of the invention the volume gauge 18 could be measured directly or indirectly by means of a level sensor, a flow meter or another device suitable for measuring the amount of lubrication leaving the lubrication unit 1.

In this embodiment the volume gauge 18 leads to a quick coupling for attaching the lubrication unit 1 to the equipment that needs lubrication.

The mobile lubrication unit 1 could e.g. be used for lubricating pitch, yaw and or main bearings in a wind turbine in that these large bearing requires a relatively large amount of grease at a relatively high pressure. But the application of the present invention is in no way limited to the field of wind turbines in that a demand for a mobile high-pressure lubrication unit also can be found in a other technical fields where moving equipment requires lubrication with high-viscous grease with a kinematic viscosity between 5 and 22, preferably between 7 and 18 and most preferred between 10 and 16 mmVs at 40°C. Fig. 2 illustrates a first cross section of a reciprocating positive displacement pump 3 according to the invention, as seen from the front.

In this embodiment of the invention the pump 3 is provided with two individual parallel coupled cylinders but in another embodiment the pump 1 could comprise one, three, four, five or more individual cylinders whereof one or more could be arranged in series.

The left piston 6 is in this embodiment illustrated in its bottom position whereto it has been forced by the left cam 22. In this position the cylinder chamber 8 in front of the piston 6 is very small and almost all the grease has been pushed out of the cylinder 7 through the lubrication outlet 9.

Once the left cam 22 continues its rotation the cam 22 will start moving upwards and because the downwards motion of the piston 6 has compressed the spring 24 the piston 6 and piston rod 5 will simultaneously also move upwards to release some of the load on the spring 24. As the piston 6 moves up the size of the cylinder chamber 8 will increase accordingly. In this embodiment the lubrication outlet 9 is provided with a one-way valve 31 to ensure that the grease in the lubrication outlet 9 is not drawn back into the cylinder chamber 8 and since the piston rod 5 blocks the lubrication inlet 4 for the most of the pistons upwards travel a forceful vacuum is created in the cylinder chamber 8.

When the radial bores 12 in the piston reaches the lubrication inlet 4 as disclosed in the right cylinder 7 this vacuum will draw a new portion of lubrication into the cylinder chamber 8 where after the cam 22 will force the piston 6 downwards so that first the fluid communication between the lubrication inlet 4 and the cylinder chamber 8 is broken and then the grease portion in the cylinder chamber 8 is pushed out of the lubrication outlet 9. To ensure that lubrication is not drawn or pushed out of the cylinders 7 each cylinder 7 is provided with a lip seal located above the lubrication inlet 4 so that it never comes in contact with the conduits 10 in the piston or the piston rod hereby ensuring its life.

In this embodiment of the invention the piston rod 5 and the piston 6 are formed integrally as one monolithic component in that the piston 6 is constituted by the front surface of the piston rod 5. However in another embodiment the piston 6 and the piston rod 5 could be formed as two separate parts e.g. connected through a joint allowing at least some rotating between the two parts e.g. if the piston rod 5 was connected to a eccentric arranged shaft. In such case the conduits 10, creating the fluid communication between the lubrication inlet 4 and the cylinder chamber 8, would only be in the piston 6. Since the piston rod 5 and the piston 6 in this embodiment are formed by the same cylindrical rod the outer diameter 14 of the piston rod 5 is equal to the outer diameter 15 of the piston 6. However in another embodiment the diameter 14 of the piston rod 5 could be different from the outer diameter 15 of the piston 6. To ensure that the pressure drop between the lubrication inlet 4 and the cylinder chamber 8 is as high as possible in this embodiment, it is important that the outer diameter 14 of the piston rod 5 is substantially equal to the inner diameter 16 of the cylinder 7 so that the clearance between the two is as small as possible. However in another embodiment the outer diameter 14 of the piston rod 5 could be very different from the inner diameter 16 of the cylinder 7 e.g. if the piston 6 and the piston rod 5 was formed as two separate parts.

As previously explained the lubrication outlet 9 is provided with a pressure gauge which ensures that the operation of the motor is stopped if the output pressure exceeds a predefined level. However, at an extra safety feature the pump 3 is in this embodiment also provided with a pressure activated pressure release valve (not shown) what will open a fluid communication between the lubrication outlet 9 and the lubrication inlet 4 if the pressure at the valve exceeds an inherent predefined activation pressure.

Fig. 3 illustrates a cross section of a piston rod 5 with axial 1 1 and radial bore 12, as seen from the front.

In this embodiment the piston rod 5 is provided with a conduit 10 in the form of one centrally arranged coaxial axial bore 11 and two transversal radial through bores 12 but in another embodiment the piston rod 5 and/or the piston 6 could be provided with another number of bores 1 1 , 12 and the bores 1 1 , 12 could be arrange differently. Fig. 4 illustrates a cross section of a piston rod 5 with channels 25 in the outer surface 13, as seen from the front.

Instead of bores the piston rod 5 and/or the piston 6 could be provided with a number of channels 25 in the surface 13 of the piston rod 5 and/or piston 6 to form the conduits 10. In this embodiment two channels 25 are provided but in another embodiment the piston rod 5 and/or the piston 6 could be provided with another number of conduits such as one, three, four or more.

Fig. 5 a mobile lubrication unit 1 fitted in a suitcase 26, as seen in perspective.

By fitting the lubrication unit 1 inside a suitcase 26 it is possible to transport the unit 1 around more easily without risking damaging the unit. The suitcase can be fitted with a Perspex plate (not shown) having openings for the container socket 29, the socket 28, the quick coupling and the input panel 20 so that the rotating and power conducting parts of the unit 1 can not be reached by the operator. Furthermore the suitcase 26 is provided with a lid (not shown).

The invention has been exemplified above with reference to specific examples of reciprocating positive displacement pumps 3, piston rods 5, pistons 6 and other. However, it should be understood that the invention is not limited to the particular examples described above but may be designed and altered in a multitude of varieties within the scope of the invention as specified in the claims.

List

1. Mobile lubrication unit

2. Motor

3. Reciprocating positive displacement pump

4. Lubrication inlet

5. Piston rod

6. Piston

7. Cylinder

8. Cylinder chamber

9. Lubrication outlet

10. Conduit

1 1. Axial bore

12. Radial bore

13. Outer surface of piston rod

14. Outer diameter of piston rod

15. Outer diameter of piston

16. Inner diameter of cylinder

17. Pressure gauge

18. Volume gauge

19. Controller

20. Input panel

21. Camshaft

22. Cam

23. Bearing

24. Spring

25. Channel

26. Suitcase

27. Coupling

28. Socket Container socket Lip seal One-way valve

Claims

1. A mobile lubrication unit (1) comprising at least one motor (2) driving at least one reciprocating positive displacement pump (3), wherein said reciprocating positive displacement pump (3) comprises a lubrication inlet (4), a piston rod (5) acting on a piston (6), which is fitted inside a corresponding cylinder (7) so that a cylinder chamber (8) is established inside said cylinder (7) in front of said piston (6), said cylinder chamber (8) being provided with a lubrication outlet (9) characterized in that said piston rod (5) and/or said piston (6) comprises at least one conduit (10) for establishing fluid communication between said lubrication inlet (4) and said cylinder chamber (8).

2. A mobile lubrication unit (1) according to claim 1, wherein said piston rod (5) and said piston (6) are formed integrally as one monolithic component.

3. A mobile lubrication unit (1) according to claim 1 or 2, wherein said at least one conduit (10) is formed as an axial bore (1 1) in said piston rod (5) and/or said piston (6), said axial bore (1 1) being in fluid communication with one or more radial bores (12).

4. A mobile lubrication unit (1) according to claim 1 or 2, wherein said at least one conduit (10) is formed as one or more channels (25) in the outer surface (13) of said piston rod (5) and/or said piston (6).

5. A mobile lubrication unit (1) according to any of the preceding claims, wherein the outer diameter (14) of said piston rod (5) is equal to the outer diameter (15) of said piston (6).

6. A mobile lubrication unit (1) according to any of the preceding claims, wherein the outer diameter (14) of said piston rod (5) is substantially equal to the inner diameter (16) of said cylinder (7).

7. A mobile lubrication unit (1) according to any of the preceding claims, wherein said lubrication outlet (9) is connected to a pressure gauge (17).

8. A mobile lubrication unit (1) according to any of the preceding claims, wherein said lubrication outlet (9) is connected to a volume gauge (18).

9. A mobile lubrication unit (1) according to claim 8, wherein said volume gauge

(18) comprises a switch arranged for being activated by a movable piston, wherein said movable piston is arranged to be moved by incoming lubrication.

10. A mobile lubrication unit (1) according to any of the preceding claims, wherein said mobile lubrication unit (1) further comprises a controller (19) comprising means for controlling the operation of said motor (2).

1 1. A mobile lubrication unit (1) according to any of claims 7 to 10, wherein said controller (19) comprises means for at least partly controlling the operation of said motor (2) on the basis of input from said pressure gauge (17) and/or said volume gauge (18).

12. A mobile lubrication unit (1) according to claim 10 or 11, wherein said controller

(19) further comprises an input panel (20) for inputting operational parameters.

13. A mobile lubrication unit (1) according to claim 12, wherein said controller (19) comprises means for at least partly controlling the operation of said motor (2) on the basis of said operational parameters.

14. A mobile lubrication unit (1) according to any of the preceding claims, wherein said mobile lubrication unit (1) has a capacity of between 0.05 and 5, preferably between 0.1 and 2 and most preferred between 0.1 and 1 litre/min.

15. A mobile lubrication unit (1) according to any of the preceding claims, wherein said motor (2) is connected to a camshaft (21) and wherein a cam (22) on said camshaft (21) drives said piston rod (5) at least in one direction.

16. A mobile lubrication unit (1) according to any of the preceding claims, wherein said cam (22) acts on said piston (6) through a bearing (23).

17. A mobile lubrication unit (1) according to any of the preceding claims, wherein a spring (24) drives said piston (6) at least in one direction.

18. A mobile lubrication unit (1) according to any of the preceding claims, wherein said motor (2) is an electric motor.

19. A mobile lubrication unit (1) according to any of the preceding claims, wherein said reciprocating positive displacement pump (3) comprises at least two pistons (6) fitted inside corresponding cylinders (7).

20. A mobile lubrication unit (1) according to any of the preceding claims, wherein said at least two pistons (6) fitted inside said corresponding cylinders (7) are arranged in parallel.

21. A method for creating a high-pressure flow of lubrication, said method comprising the steps of:

• forcing a piston (6) in a direction out of a corresponding cylinder (7) so that a vacuum is created in a cylinder chamber (8) in front of said piston (6) inside said cylinder (7),

• subsequently creating a fluid communication between a lubrication inlet (4) and said cylinder chamber (8) so that said vacuum draws a lubrication portion from said lubrication inlet (4) and into said cylinder chamber (8) through a conduit (10) in a piston rod (5) driving said piston (6) and/or through a conduit (10) in said piston (6), and

• forcing said piston (6) in a direction into said cylinder (7) so that said lubrication portion is forced out of said cylinder chamber (8) through a lubrication outlet (9).

22. A method according to claim 21 , wherein said fluid communication is cut off at the first part of said piston's (6) travel into said cylinder (7).

23. A method according to claim 21 or 22, wherein said lubrication is a high- viscous grease with a kinematic viscosity between 5 and 22, preferably between 7 and 18 and most preferred between 10 and 16 mm²/s at 40°C.

24. A method according to any of claims 21 to 23, wherein said piston (6) is forced in a direction into said cylinder (7) by means of a rotating camshaft (21).

25. A method according to any of claims 21 to 24, wherein said piston (6) is forced in a direction out said cylinder (7) by means of a spring (24).

26. A method according to any of claims 21 to 25, wherein the operation of said piston (6) at least partly is driven by a motor (2).

27. A method according to claim 26, wherein the operation of said motor (2) is controlled by a controller (19) at least partly on the basis of inputs regarding desired lubrication output pressure and/or desired output lubrication volume.

28. A method according to claim 26 or 27, wherein the operation of said motor (2) is controlled by a controller (19) at least partly on the basis of inputs regarding actual lubrication output pressure and/or actual output lubrication volume.

29. A method according to any of claims 26 to 28, wherein said controller (19) will stop the operation of said motor (2) if a measurement of said actual lubrication output pressure exceeds a predetermined maximum lubrication output pressure.

30. A method according to any of claims 26 to 29, wherein said controller (19) will stop the operation of said motor (2) if a measurement of said actual lubrication output volume exceeds or is equal to a desired output lubrication volume.