fig5 illustrates a tractor 1 with an attached implement 2 . the implement 2 may be a large - bale press . the implement 2 is pulled by the tractor 1 and driven by the power take - off shaft 4 of the tractor 1 . thus , a driveshaft 3 is provided which , at one end , is connected to the power take - off shaft 4 . the other end of the driveshaft 3 is connected to the driving journal 6 of the implement 2 . the driveshaft 3 is associated with a torque limiting coupling 5 . the coupling is to prevent any damage in the case of overloading , for example , if the implement 2 is clogged up . the torque flow between the power take - off shaft 4 and the driving journal 6 and vice versa is interrupted by the coupling . various embodiments of the torque limiting coupling 5 will be described in greater detail with reference to fig1 to 4 . fig1 and 2 illustrate a first embodiment of a torque limiting coupling . the coupling includes a coupling hub 7 with a central bore 8 centered on a longitudinal axis 13 . the central bore 8 is designed as a through - bore , with one portion of the bore 8 having splines in order to establish a torque connection with a driving journal . also , the bore 8 has a hollow cylindrical seat portion 20 with an enlarged diameter . the coupling hub 7 has a first portion 9 whose diameter is increased relative to the bearing seat 18 . the first portion 9 has a cylindrical outer face 12 which is laterally delimited by the two side faces 10 and 11 . first recesses 14 are provided in the first portion 9 . the first recesses are slot - shaped and start from the outer face 12 . the first recesses central axis extends parallel to a face containing the longitudinal axis 13 . in the present embodiment , each first recess 14 is associated with a second recess 15 . the first recess 14 is associated with a driving member 17 . the driving member 17 is in the form of a slide . the driving member 17 is adjustable from a position in which it projects beyond the outer face 12 into a withdrawn position in which it is positioned inside the contour of the outer face 12 . a cylindrical bearing seat 18 , arranged next to the first position 9 , serves to receive the inner race of a rolling contact bearing 19 . the seat portion 20 of the coupling hub is associated with a stepped journal 21 . the journal 21 has a cylindrical bearing face 22 whose diameter is reduced relative to the seat portion 20 . a rolling contact bearing 23 is positioned on the journal 21 by its inner race . the driving members 17 , at their ends adjustable beyond the outer face 12 of the coupling hub 7 , each have a torque transmitting face 24 . the face 24 extends at an angle . at its inner end positioned in the first recess 14 , the driving members 17 include two first switching faces 25 , 26 . the first switching face 25 is loaded by a second switching face 28 of a switching cam 27 . the first switching face 25 supports the driving member 17 in the torque transmitting position . the further first switching face 26 of the driving member 17 and the further second switching face 29 of the switching cam 27 are in contact with one another when the driving member 17 is in the disconnected position , where it is withdrawn into the first recess 14 . the switching faces 25 , 26 and 28 , 29 , respectively , extend in such a way that a spring assembly 30 , loading the switching cams 27 and positioned in the second recess 15 , either applies a sufficiently high supporting force for the driving members 17 in the torque transmitting position or loads the driving members with a reduced force . the spring assembly 30 arranged in the second recess 15 is supported against a screw 31 threaded into an inner threaded portion 16 of the second recess 15 . thus , it is also possible to adjust the force of the switching cams 27 acting on the driving members 17 . the coupling sleeve 32 is supported on the rolling contact bearings 19 , 23 . the coupling sleeve bore 33 is arranged around the coupling hub 7 . four grooves 34 are provided on the bore to receive the heads of the driving members 17 . the heads 36 project beyond the outer face 12 in the torque transmitting position . supporting faces 35 extend in the grooves 34 to support the torque transmitting faces 24 of the driving members 17 . the driving members 17 , by their head faces 36 , enter the grooves 34 far enough to almost completely fill the grooves 34 . the coupling sleeve 32 has a cover 37 which fully covers the end face 45 of the coupling sleeve 7 . the coupling sleeve 32 has a bearing bore 39 which supports the outer race of the rolling contact bearing 23 . the cover 37 is connected by a weld 42 to the coupling sleeve 32 . the cover carries the yoke arms 41 of a universal joint . an annular groove 43 is arranged close to the rolling contact bearing 23 in the cover 37 . the cover 37 , by means of its inner face , is positioned opposite the side face 10 of the coupling hub 7 . the coupling sleeve 32 has a further cover 38 which is received and centered in a bore 46 arranged in front of the bore 33 . an annular groove is provided in the outer face of the cover 38 . the annular groove accommodates a sealing ring 47 and effects an oil - proof connection relative to the coupling sleeve 32 . the cover 38 is held by a securing ring 55 secured at the coupling sleeve 32 . thus , in the direction of the longitudinal axis 13 , the coupling 7 , by its first portion 9 and its two side faces 10 , 11 , is guided between the covers 37 , 38 . the cover 38 has a bearing bore 40 to receive the outer race of the rolling contact bearing 19 . the cover 38 has a receiving bore 49 for a shaft sealing ring 48 . the sealing ring 48 has a sealing effect relative to the bearing seat 18 of the coupling hub 7 . the cover 38 also includes an annular groove 44 in its inner face pointing towards the side face 11 . however , the annular groove 44 is arranged on a greater diameter than the annular groove 43 of the cover 37 . the cover 37 , additionally , has a filling aperture 50 which is closed by threaded plug 51 . the filling bore 50 is used to introduce oil into the inner space delimited by the coupling hub 7 , the coupling sleeve 32 and the covers 37 , 38 . when , as illustrated , the torque limiting coupling rotates around the longitudinal axis 13 in the torque transmitting position , the driving members 17 , as illustrated , engage the grooves 34 . if the load occurring is such that the driving members 17 move inwardly out of the grooves 34 , the first switching face 26 and the second switching face 29 come into contact with one another . at the same time , if rotation continues , the oil contained in the remaining spaces , for example in the annular grooves 43 , 44 and the first recesses 14 , is able to reach the grooves 34 and fill the grooves . during the relative rotation occurring between the coupling sleeve 32 and the coupling hub 7 , the driving members 17 , via their heads , slide over part of their range of movement at the wall of the bore 33 and on the oil of the grooves 34 . while the rotational speed continues to be high , the driving members 17 cannot enter the grooves 34 and displace the oil because the respective force is reduced due to the support provided by the switching faces 26 and 29 . only when the rotational speed is reduced , can the oil be displaced out of the grooves 34 by the driving members 17 . then , the driving members can move into the torque transmitting position . as a result of the gaps existing between the driving members 17 and the first recesses 14 and at the ends between the side faces 10 , 11 and the covers 37 , 38 , it is possible to achieve an additional damping effect when the driving members 17 enter the grooves . this is caused by the oil escaping inwardly through the gaps in order to reach the annular grooves 43 , 44 and the free spaces of the first recesses 14 underneath the driving members 17 and the second recesses . if necessary , additional channels for guiding the oil in a specific direction may be provided . the behavior of the torque limiting coupling can be influenced by selecting oil viscosity and by determining the amount of oil present in the torque limiting coupling . fig3 shows a second embodiment of a torque limiting coupling . the coupling hub 7 ′ has a toothed through - bore 8 ′. the hub 7 ′ has a central portion in which the driving members 17 ′ are guided . furthermore , the coupling hub 7 ′, at each of its ends , has a seat face which receives two rolling contact bearings . one cover 37 ′ is firmly connected to the coupling sleeve 32 ′. the other cover 38 ′ is positioned in the bore 33 ′ of the coupling sleeve 32 ′ and is held by a securing ring . the first cover 37 ′ is connected to the coupling sleeve 32 ′ by a weld 42 ′. both covers 37 ′, 38 ′, on their inner faces , have annular grooves 43 ′, 44 ′ which are arranged on the same diameter . the fixed cover 37 ′ has a filling bore 50 ′ which ends in the region of the annular groove 43 ′ and is closed by a plug . the loose cover , in its outer circumferential face , has an annular groove which is engaged by a sealing ring 47 ′ which serves to seal the unit to make it oil - proof . further , shaft sealing rings 48 ′ are accommodated in both covers 37 ′, 38 ′ on one side of the rolling contact bearings . the shaft sealing rings have a sealing function relative to the coupling hub 7 ′. each driving member 17 ′ is loaded by two spring assemblies 30 ′. fig4 finally , shows a third embodiment where the coupling sleeve 32 ″ is associated with two covers 37 ″, 38 ″. the covers 37 ″, 38 ″ accommodate and guide the first portion of the coupling hub 7 ″. the outer face 12 ″, while cooperating with the bore 33 ″ of the coupling sleeve 32 ″, serves to support the coupling hub 7 ″. on their inner faces , the two covers 37 ″, 38 ″ each have two coaxially arranged annular grooves 53 , 54 and two further annular grooves which serve to receive sealing rings 47 ″. the two covers are pressed against the side faces of the coupling sleeve 32 ″ via the sealing rings 47 ″. circumferentially distributed screws 52 are provided to tension the covers 37 ″, 38 ″ against the coupling sleeve 32 ″. shaft sealing rings 48 ″ are arranged between the two covers 37 ″ and 38 ″ and the coupling hub 7 ″. the shaft sealing rings 48 ″ render the unit oil - proof . oil is also provided in the unit . while the above detailed description describes the preferred embodiment of the present invention , the invention is susceptible to modification , variation and alteration without deviating from the scope and fair meaning of the subjoined claims .