detailed embodiments according to the present disclosure are described herein . it is to be understood , however , that the disclosed embodiments are merely examples , and that other embodiments may take various and alternative forms . the figures are not necessarily to scale ; some features may be exaggerated or minimized to show details of particular components . therefore , specific structural and functional details disclosed herein are not to be interpreted as limiting , but merely as a representative basis for teaching one skilled in the art to variously employ the present invention . fig1 shows a road finishing machine 1 with a screed 2 and a material bunker 3 provided in the front , seen in the paving direction f , for receiving paving material . a pushing device 4 in accordance with the disclosure is provided in front of the material bunker 3 . the pushing device 4 is mounted at the chassis 5 of the road finishing machine 1 . in particular , the pushing device 4 is fixed to a transverse member 6 of the chassis 5 . fig2 shows the pushing device 4 separate from the road finishing machine 1 in an enlarged perspective representation . the pushing device 4 has a docking assembly 7 and first and second absorber units 8 . the two absorber units 8 are fixed to the transverse member 6 of the chassis 5 . the docking assembly 7 is mounted to be movable relative to the transverse member 6 of the chassis 5 . the docking assembly 7 may be moved towards the transverse member 6 and away from it . if a load l is acting on the docking assembly 7 from the front on one side , the assembly may also be inclined with respect to the transverse member 6 , as is shown in fig2 . according to fig2 , the docking assembly 7 is embodied as transverse beam which supports two rotary pushing rollers 9 . the pushing rollers 9 may dock at rear wheels of a truck which pours paving material into the material bunker 3 of the road finishing machine 1 . thanks to the pushing device according to the disclosure , such material transfer is possible during a paving drive without any paving defects occurring in the paving section . fig2 also schematically shows a sensor unit 38 which is operatively linked to a signal device . the sensor unit 38 is configured to detect a position of the pushing device 4 and forward it to the signal device 39 from which a docking position and / or docking maneuvering instructions may be displayed to the operator of the road finishing machine and / or the truck . fig3 shows the assembly of the absorber unit 8 according to the disclosure in an extended position . the absorber unit 8 is in fig3 fixed to the transverse member 6 of the chassis 5 and includes a piston - cylinder unit 10 . the piston - cylinder unit 10 is a closed differential cylinder with a cylinder 11 and a working piston 12 mounted in a prestressed manner in the cylinder 11 . in the cylinder 11 , a pre - compressed fluid 13 is provided which prestresses the working piston 12 in the extended position . the prestressed fluid 13 pushes the working piston 12 against a piston bearing 14 . the piston bearing 14 is screwed into the cylinder 11 and closes the cylinder 11 to the outside . a valve 15 is provided in the piston bearing 14 . through the valve 15 , the cylinder 11 of the piston - cylinder unit 10 may be filled with the fluid 13 . by filling in the fluid 13 , a predetermined pressure may be applied to it , so that it is present in the cylinder 11 in a prestressed or compressed state and thus stores a compression force by which the working piston 12 may be held in the extended position . the working piston 12 has a piston rod 16 and a piston plate 17 . the piston rod 16 is guided in the piston bearing 14 and seals the piston - cylinder unit 10 together with the piston bearing 14 . the piston plate 17 has a slightly smaller diameter than the inner diameter of the cylinder 11 , a plate seal 18 being provided at the periphery of the piston plate 17 . the plate seal 18 prevents the prestressed fluid 13 from flowing , during a movement of the working piston 12 , into the cylinder 11 or out of it externally past the piston plate 17 . the piston - cylinder unit 10 moreover has a mounting flange 19 which is provided for fixing the piston - cylinder unit 10 at the transverse member 6 of the chassis 5 . the docking assembly 7 is fixed to the piston rod 16 of the working piston 12 . the distance between the docking assembly 7 and the mounting flange 19 represents a damping path x . fig3 shows that the docking assembly is positioned in an extended position in which the working piston 12 is pressed against the piston bearing 14 by the prestressed fluid 13 . if the working piston 12 is pressed into the cylinder 11 by a force l applied externally at the docking assembly 7 , the docking assembly 7 will move towards the mounting flange 19 . simultaneously , the compression force present in the cylinder 11 due to the prestressed fluid 13 will increase because the volume of the working piston 12 in the cylinder 11 will increase . fig3 also shows that two flow channels 21 are provided in the piston plate 17 . when the working piston 12 is pressed into the cylinder 11 , the fluid 13 will be forced to flow through the flow channels 21 . in the process , the fluid will be displaced from the first chamber right of the piston plate 17 into the second chamber left of the piston plate 17 . when the working piston 12 is returned , the fluid 13 will flow back into the first chamber . fig4 shows the absorber unit 8 according to the disclosure in a retracted position , wherein the docking assembly 7 is pushed against the mounting flange 19 . in fig4 , the working piston 12 has passed the complete damping path x , whereby the docking assembly 7 is lying against the mounting flange 9 . here , the working piston 12 is inserted in the cylinder 11 corresponding to the length of the damping path x . the compression force onto the fluid 13 prestressed in the cylinder 11 has thereby increased , whereby additional energy is stored in the fluid 13 . in fig4 , the load l applied from outside is higher than the force f originally applied by the prestressed fluid 13 . thereby , the working piston 12 is pushed into the cylinder 11 . the working piston 12 is completely returned to its original position according to fig3 if the force l acting from outside falls below the compression force f originally applied by the fluid 13 . the working piston 12 will then travel back to the extended position , as is shown in fig3 . fig5 shows a particular embodiment of the absorber unit 8 according to the disclosure . the absorber unit 8 has a guiding section 22 . the guiding section 22 forms an extension of the cylinder 11 . the guiding section 22 has a guiding piston 23 which is screwed onto the working piston 12 . the guiding piston 23 has a mounting piece 24 which may be coupled to the docking assembly 7 . the guiding section 22 furthermore has a cylinder section 25 which is an extension of the cylinder 11 and receives the guiding piston 23 so that the latter is movable within it . in the cylinder section 25 , a guiding bushing 26 is provided . the guiding bushing 26 lines the cylinder section 25 and takes care of a uniform sliding motion of the guiding piston 23 . furthermore , a vent hole 27 is provided in the guiding section 22 which is formed at the bottom of the guiding section 22 in the cylinder section 25 . as an alternative or in addition , the vent hole 27 could also be formed in the guiding piston 23 . according to fig5 , the guiding bushing 26 is secured in the guiding section 22 by a scraper 28 . the scraper 28 takes care that the guiding bushing 26 does not slip out of the guiding section 22 during a movement of the working piston 22 . the scraper 28 may be designed as a shaped ring and engage in a mounting of the cylinder section 25 . fig5 furthermore shows that the mounting flange 19 is welded to the guiding section 22 . by means of several screw connections , the mounting flange 19 is fixed to the transverse member 6 . the mounting flange 19 is made of a rectangular sheet preferably having the following dimensions : 173 mm × 160 mm × 30 mm . in the mounting flange 19 , 4 bores are preferably provided . these preferably have a diameter of 18 mm and a hole circle diameter of 110 mm . preferably , the mounting flange 19 is attached to the transverse member 6 by means of hexagon bolts 29 . for assembling the guiding piston 23 , a mounting bore 30 is provided in the piston rod 16 of the working piston 12 , which , in the extended position of the working piston 12 , is aligned with a tapped bore 31 which is provided in the guiding section 22 . during the assembly of the guiding piston 23 , a bolt is pushed through the tapped bore 31 and the mounting bore 30 , so that the working piston 12 is fixed relative to the guiding section 22 . the guiding piston 23 may then be firmly screwed onto the piston rod 16 of the working piston 12 . after screwing and securing , the bolt is removed again . the tapped bore 31 is covered by the transverse member 6 and therefore protected from soiling . in the piston plate 17 of the working piston 12 , two one - way valves 32 are provided . the latter may be transferred to an open position when the working piston 12 pushes into the cylinder 11 . with a restoring movement of the working piston 12 , they will then close automatically , so that the fluid 13 may only flow back through the flow channels 21 . this permits to provide only little resistance against the working piston 12 when it is retracted into the cylinder 11 , where higher resistance will act against the restoring movement of the working piston 12 . hence , the working piston 12 is slowly moved back into its original position in the extended position . with reference to fig5 , the piston rod 16 of the working piston 12 preferably has a diameter of 30 mm . the damping path x is preferably 80 mm . the initial force onto the working piston 12 applied by the prestressed fluid 13 is preferably within a range of between 200 n and 800 n , but in particular 300 n or 700 n . the blocking force , i . e ., the maximum compression force by the fluid 13 which is reached when the working piston 12 has covered the complete damping path x , i . e ., when it is completely retracted , is preferably within a range of between 7500 n and 8500 n , in particular , however , 8000 n or 8300 n . the diameter of the guiding piston 23 is preferably 90 mm . the guiding piston 23 is screwed onto the piston rod 16 of the working piston 12 . by means of a tension pin 33 , the guiding piston 23 is secured on the piston rod 16 . the guiding bushing 26 preferably has dimensions of 90 mm × 98 mm × 118 mm . in operation , when a load l from outside acts on the docking assembly 7 , the guiding piston 23 retracts into the piston - cylinder unit 10 together with the working piston 12 , the working piston 12 immersing into the prestressed fluid 13 . the prestressed fluid 13 originally exerts a pressure within a range of 30 bar to 110 bar onto the working piston 12 , where it in particular applies a pressure of 43 bar ( 300 n ) or 99 bar ( 700 n ). caused by the one - way valves 32 in the piston plate 17 , the working piston 12 retracts with relatively low resistance and compresses the prestressed fluid 13 across the spring trajectory by a certain bar value until the blocking force is reached . when the load l acting from outside is removed , the one - way valves 32 will be closed and the working piston 12 together with the guiding piston 23 slowly returns to the extended position because the fluid 13 is now , while it is returning , only forced through the smaller flow channels 21 . the returning speed depends on the diameter of the flow channels 21 which may be of different sizes or be variable , depending on the embodiment . according to a particular embodiment , a proximity sensor 34 may be fixed in the above - mentioned tapped bore 31 , which is used for assembling the guiding piston 23 , the proximity sensor being embodied for detecting the docking of a load to the docking assembly 7 by detecting an insertion of the guiding piston 23 into the guiding section 22 . the proximity sensor 34 may be operatively linked to a non - depicted signal device of the road finishing machine 1 by which the docking of a truck to the pushing device 4 according to the disclosure may be displayed to a driver of the road finishing machine 1 and / or a driver of the docked truck . fig6 shows the working piston 12 with the piston rod 16 and the piston plate 17 . in the piston plate 17 , the one - way valves 32 are designed as ball valves . within the one - way valves 32 , the flow channels 21 are provided . the piston plate 17 comprises the plate seal 18 along its circumference . the piston rod 16 has a first threaded section 35 onto which the guiding piston 23 may be screwed , and a second threaded section 36 provided at the opposed end . a screw nut 37 fixes the piston plate 17 on the threaded section 36 . fig6 also shows the mounting bore 30 for fixing the working piston 12 during the assembly of the guiding piston 23 . fig7 shows a force - displacement graph for an absorber unit according to the disclosure . an initial force of 300 n acting on the working piston 12 in the extended position and a blocking force of 8000 n acting on the working piston 12 in the retracted position are characteristic when the working piston 12 has covered the complete damping path x . according to fig7 , the damping path x is 80 mm . here , a spring rate of 962 . 5 n / mm results . by the pushing device according to the disclosure , high loads may be excellently cushioned , while an energy increase may be easily stored and released again in a controlled manner by it . with the pushing device according to the disclosure , it is possible to slow down trucks docking to it without any accelerations being transmitted to the road finishing machine by the docking operation . after the material transfer , the truck may be easily undocked , whereby the pushing device according to the disclosure returns to its original position . according to the disclosure , the pushing device 4 may just as well be provided at a charger vehicle which docks to a truck for material transfer . while exemplary embodiments are described above , it is not intended that these embodiments describe all possible forms of the invention . rather , the words used in the specification are words of description rather than limitation , and it is understood that various changes may be made without departing from the spirit and scope of the invention . additionally , the features of various implementing embodiments may be combined to form further embodiments of the invention .