DRIVE ROLLER ARRANGEMENT

Abstract: The invention relates to a drive roller arrangement of the type in which it is possible to fold down a drive roller, freely mounted on a shaft (8), into engagement with a driven and a non-driven wheel on a vehicle. The invention makes this arrangement more compact because the roller shaft (8) mounted at the ends of the forearms (6) mounted in a elbow joint (7) on hydraulically operated (9) upper arms (5), mounted on a shaft (4) fixed to the vehicle, is caused in a retracted position to swing in towards the upper arms (5). This is done by providing a forearm (6) with a guide surface (10), which interacts with a deflector (11) placed outside the circular arc described by the elbow bearings (7) as it swings.

Description: Drive Roller Arrangement The invention relates to a drive roller arrangement with a drive roller which can be engaged and disengaged with a driven and a non-driven wheel in a vehicle, and comprising a first shaft fixed in the vehicle, two upper arms pivotable about said first shaft by means of a hydraulic cylinder, two forearms pivotable in elbow bearings at the free end of the upper arms, said drive roller being rotatably mounted on a second shaft which is attached to the free ends of the forearms, forced guidance means being disposed, when the upper arms swing from the engagement position, to fold the forearms towards the upper arms. Drive roller arrangements with drive rollers are previously known and have been extensively sold by us under the name "Robson Drive . Two such drive arrangements are mounted on either side of a truck for example, making it possible when engaged to transmit the wheel pair driven by the engine and the transmission to the non-driven wheel pair. When driving on difficult surfaces, e.g. transporting lumber in the forest, traction can be increased appreciably thus reducing the risk of becoming stuck. In an older known design of a drive roller arrangement, the forearms, in the disengaged position, hang with their roller straight down from the elbow bearing. This is no particular disadvantage if there is plenty of space for mounting the arrangement, and if the forearms can be made short. Otherwise there is the risk that the roller will swing against one of the vehicle wheels. To eliminate this disadvantage forced guidance means have been arranged so that when the upper arm is swung upwards, the forearm is forced upwards, thus further retracting it and the roller attached thereto. This attempt to achieve a more compact arrangement has, however, the disadvantage that the elbow joint may become stuck because of thickening of the grease in the bearing and/or ice, snow and frozen dirt preventing the movement of the elbow joint. There is thus the risk s that when the roller is moved downwards, it will end up so - high on one of the wheels that it will not engage both wheels. It is a purpose of the invention to achieve a drive roller arrangement which is more compact and still does not have the disadvantages mentioned, and which is suitable for installation even where the space is limited. It is desirable to have the smallest possible displacement, preferably limited only by the length of stroke of the vchicle wheel suspension, since the drive roller arrange ment is normally fixed to the suspened portions of the -vehicle. These and other purposes are achieved according to the invention by a construction of the type mentioned by way of introduction whichis characterized in that a forearm is provided at:the elbow bearing with a projection which points cssentially directly away from the drive roller shaft and is of sufficientlength that whenthe upper arm moves towards the engagement position, it comes into S with an abutment, thus actuating the forearm sofas; ; to fold it out, whereby, due to the pivoting of the projec tion and the forearm rigidly joined thereto about the elbow j bearing, the projection is moved out of the way; and can clear the abutment . This avoids the disadvantage of having the elbow joint stick, and thus having the roller',' when moving towards engagement, only engage one of the wheels high up on the wheel, so that the wheel rotation, prevents 'the drive roller from engaging both of the vehicle wheels. 0 In accordance with an especially preferred embodiment, said forced guide means consist in that at least one of the forearms is provided with a guide surface which is non parallel to the line connecting the scond shaft and the elbow bearing, and that a deflector fixed to the vehicle, preferably identical with said abutment, is mounted outside the circular arc which the elbow bearing describes as the upper arm pivot and is disposed during said pivot movement to interact with the guide surface and swing the forearm to a non-vertical position in towards the upper arms. According to another preferred embodiment, a second abutment is fixed to the vehicle inside the circular arc described by the elbow bearing during the pivot movement of the upper arm and is disposed in the disengaged position of the drive roller arrangement, to abut against said forearm on the opposite side to the deflector, so that the forearm becomes fixed between the second abutment and the deflector. In order to obtain a construction which is as compact as possible, and especially to avoid the necessity of having the first shaft pass through the entire vehicle and be common to the drive roller arrangements on both sides of the vehicle, it is suitable that each drive roller arrangement be made very stable, so that the first shaft can be fixed at a high location therein and so that the drive roller arrangement can be fastened to a vehicle chassis points substantially lower than the first shaft. It is then suitable to place a vehicle-fixed and essentially downward- ly directed girder means adjacent to the vehicle chassis but with the first shaft fixed to its upper portion. This girder can be a U-girder or two parallel plates welded together at the upper and lower ends, with the hydraulic cylinder being suitably mounted with one end at the lower end of the girder means and partially enclosed therein, and actuating a lever rigidly fixed to the upper arms and pivotable about the first shaft and forming an obtuse angle with the upper arms. Thus very compact arrangements are obtained, so that two mirror-reversed drive roller arrange ments can be mounted on either side of a vehicle using only the lower port,ion of-the vehicle frame, Which can be suitably reinforced with tie-rods fixed in the girder means. The invention will now be described in more detail with reference to the figures. Fig 1 shows a drive roller arrangement with the drive roller in engagement with two vehicle decks (only partially indicated). Fig 2 shows an inner pair of arms in a drive roller arrangement according to one embodiment' of the invention in which the drive roller (not shown) is retracted upwards. Fig 3 shows schematically an alternative embodiment, showing the inventive function. Figs 4 and 5 show prospective views of a drive roller arrangement. The drive roller 1 shown in Fig 1 is disposed in an opera X pysition: between two vehicle wheels, of which only portions of the tires are visible. The roller 1 is-frefely; rotatably mounted on a shaft 8 which is fixed at both ends in arms 6, the outer one of which is visible in the figure. These forcarms 6 are mounted via elbow bearings 7 on the free ends of the upper' arms;5,sswhich are in turn pivotally; mounted on a shaft 4 fixed to the vehicle. As can be seen even more clearly in Fig 2, the arm 5 can rotate about the shaft 4 with the aid of a hydraulic cylinder 9 via a lever 16 rigidly joined to the arm 5. By actuation by the hydraulic cylinder 9, the elbow bearing 7 and with it the bearing 8 of the drive roller can be moved downwards to the engagement position shown in Fig. 1. It sbould,be; noted, that the required downwa-rd forces -on 0 the roller 1 ,to achieve the desired coupling betweenXthef wheels 2 and 3 are considerable. It has therefore previously been usual to have the forces from the drive rollers, which are mounted on either side of the vehicle, be absorbed by a rather thick shaft 4 mounted in the vehicle and passing through it. However, this shaft must be rather highly placed, and in accordance with a preferred embodiment, a shaft 4 is therefore arranged on each side of the vehicle. In order to achieve the required force absorption and still achieve a sufficiently high placement of the shaft 4, one can proceed as follows The end of the shaft 4 pointing towards the vehicle is provided with a U-girder, half of which is shown as 15 in Fig 2. The distance between these halves is 15-20 cm, and they are joined at the top at the shaft 4 and at the bottom at a shaft 14. The inner half is fixed to the vehicle chassis. The chassis is reinforced by a pair of through-tie-rods at different heights, which join the inner halves on either side to each other. It is thus possible to absorb the forces pressing on the rollers, which will act as bending forces on the shafts 4, and thus there is no need of having a shaft passing transversely through the vehicle as highly placed as the shafts 4. The hydraulic cylinder 9 and the lever 16 are arranged between the two parallel U-girder legs. Figs 4 and 5, in which the same reference numerals have been used as in the other figures, reveal this arrangement even more clearly, showing a drive roller arrangement in perspective, in the former from the outside, in the latter from the side facing the vehicle. The U-girder 15 is welded to another girder 17 into a stable frame which is capable of holding the shaft 4 fixed therein. Mounting points 18, 19 and 20 are arranged for fastening to the vehicle frame. It is suitable to arrange through-tie-rods fixed to the points 19 and 20 and to corresponding points on a reversed drive roller arrangement on the opposite side of the vehicle frame. In the retracted position, which is shown in Fig 2, it is evident that the arms 6 (only the inner one of which is shown in the figure) can be swung upwards towards the upper arms- 5. This- is achieved by the interaction between a projection fixed to the inner forearm 6, and having; a guide surface 10 which forms an angle with the longitudinal direction of the forearm 6, and a deflector 11 fixed to the vehicl. This deflector must be placed so -that the 'elbow joint clears it when the upper arm 5 is swung downwards. To prevent the upper arm 5 and the forearm 6 from remain ing at the same angl as shown in Fig 2, when the upper arm is swung downwards (this can be caused by the bearing 7 becoming stuck because of lubricant thickening or cold) the forearm is provided with a projection 12. This is ; placed so that when the upper arm is swung downwa,-rd,s,- the; projction 12 will hook the deflector 11 and continued swinging down of the upper arm 5 will cause the elbow joint to unfold. This guarantees that the drive roller will actually come into engagement against both of the vehicle whcels and not end up in a high position only in coniact with one of the wheels, in which case the movment of the whcel could-e'asily prevent engagement in the correct position. If the forearms 6 end up in such a position that the shaft 8 is above a straight line joining the the bearing 7,, an'd the vehicle wheel shafit,;it will, be entirely impossible to place the drive roller in place, even if the vehicle is stationary, and if the vehicle is 0 rolling, this will furthejr displace the criti-cal point downwards. The design with the projection 12 interacting with the deflector 11 prevents such mishaps. An abutment 13 fixed to the vehicle is arranged so that whn the system is in the retracted position, the forearm 6 will be pressed between the;;fixeddeloments 11 and 13. Thus the forearm 6 will be fixed against rotation in either dirction about the shaft 7. It is preferable, but not entirely necessary, to have the deflector 11 serve both to deflect the forearm 6 during retraction and to fold out the forearm 6 during engagement. A number of alternative solutions are, however, possible,for example the solution shown schematically in Fig 3, in which the functions of the guide surface 10 and the pro jection 12 have been assumed by the projection 12t which is an extension of the arm 6, while the vehicle-fixed deflector 11 has been replaced by a "fork cam" 41', r so constructed that the projection 12' with a roller 12" interacts therewith during retraction and is taken into its fork, and which then causes the desired unfolding for engagement of the roller. It is obvious that the person skilled in the art, after studying the invention, can suggest a variety of alternative and equivalent solutions to the problems solved by the invention. The invention provides a drive roller arrangement which is quite compact, and therefore it is possible to equip even special trucks with it, which was previously impossible due to lack of space. The older and previously known drive roller arrangements have primarily been used in lumber trucks which are often driven on poor forest roads where the risk of becoming stuck is considerable. A larger portion of the vehicle park can now enjoy the advantages of drive rollers by virtue of the invention

Claims: CLAIMS 1 Drì0veSroller arrangement with w drive roller, t; which can be engaged nnd disengaged with a driven and a non driven wheel (2,3) in a vehicle, and comprising a first shaft (4) fixed in the vehicle, two upper arms (5) pivot v able' about said' first shaft by means of a hydraulic - cylinder (9), two forearms (6) pivotable in elbow bearings (7) at the free ends of the upper arms, said drive roller ; ; being rotatably mounted, on a second shaft (8), which is attached to the free ends of the forearms, forced guidance means being disposed, when the upper arms swing from the engagement position, to fold the forearms (6) towards the upper arms, characterized in that a forearm is provided at the elbow bearing with a projection (12) which points substantially directly away from the drive roller shaft (8) and is of sufficient length so that when the upper arm movs towards the engagement position it comes into-contact with-an abutment (11), thusXactuSating; the forearm so as to fold it out, whereby, and due to the pivoting of the projction and the forearm rigidly joind thereto about the elbow bearing, the projction is moved out of the way and can clear the abutment. 2. Drive roller arrangement according to Claim 1, characterized in that said forced guidance means consist in that at least one of the forearms is provided with a guide surface (10) which is non-paraallel to the line conncting the second shaft (8) and the lbow bearing (7), and that a deflector fixed tóXthefvehicle, preferably identical to said abutment (11), is mounted outside the circular arc described by the elbow bearing as the upper arm pivots, and is disposed during said pivot movement to interact with the guide surface and swing the forearms to a non-vertical position in towards the upper arms. 3. Drive roller arrangement according to Claim 1 or 2, characterized in that a second abutment (13) is fixed to the vehicle inside the circular arc described by the elbow bearing during the pivot movement of the upper arm and is disposed, in the disengaged position of the drive roller arrangement, to abut against said forearm on the opposite side to said deflector, so that the forearm becomes fixed between the second abutment and the deflector. 4. Drive roller arrangement according to one of the preceding claims, characterized in that the hydraulic cylinder (9) is mounted between, on the one hand, a first pivot bearing (14), which is mounted at the lower end of a downwardly directed supporting arm (15) fixed to the vehicle and to the first shaft 14), and, on the other hand, a lever (16) rigidly joined to the upper arms (5) and pivotable about the first shaft (4) and forming an obtuse angle with the upper arms.

Inventors: BLOMQVIST, HAKAN
Applicants: AB ZETTERBERGS MEK. VERKSTAD
Application year: 1983
Main classification: B60K25
IPC codes: B60K25, B60K17