STEERING DEVICE FOR A TRANSPORT VEHICLE

Abstract: A steering device for a transport vehicle (1) with at least one front wheel (2, 3) and at least one rear wheel (4, 5), each wheel being suspended to pivot about a steering axis (6), which lies essentially perpendicular to the supporting surface on which the wheels (2, 3, 4, 5) are intended to roll. At least one of the front wheels (2, 3) is coupled via a front tie rod (7) to an operating means (12) in such a manner that pivot movements of the operating means (12) in one plane are converted via the front tie rod (7) into steering movements of the front wheel (2, 3). At least one of the rear wheels (4, 5) is coupled via a rear tie rod (8) to a transmission means (18), which is disposed to be actuated by movements of the operating means (12) to achieve steering movements in the rear wheel (4, 5). The transmission means (18) is coupled to the operating means (12) via a linkage system (16) for transmission of torsional movements of the operating means (12) to steering movements of at least one rear wheel (4, 5), independently of the pivot movements of the operating means (12).

Description: Steering device for a transport vehicle The invention relates to a steering device for a transport vehicle with at least one front wheel and at least one rear wheel, each wheel being suspended for turning about a steer¬ ing axis, essentially perpendicular to the supporting surface 5 on which the wheels are intended to roll, at least one of the front wheels being coupled via a front tie rod to an opera¬ ting means in such a manner that pivot movements of the operating means in a plane are transmitted via the front tie rod to steering movements of the front wheel, at least one of 10 the rear wheels being coupled via a rear tie rod to a trans¬ mission means, disposed to be actuated by movements of the operating means to effect steering movements of the rear wheel. 15 Four-wheeled transport vehicles with steering devices are previously known (cf for example US-A-3 408 089), where the front wheels and the rear wheels are turned in different directions to facilitate taking sharp curves of short radii. When operating in confined spaces it can, however, be diffi- 20 cult, even with vehicles with this type of steering coupled to the front and rear wheels, to place and direct the vehicle in the desired manner. The purpose of the invention is to provide a steering device 25 for a transport vehicle of the type described by way of introduction having improved maneuverability, and according to the invention this is achieved by virtue of the fact that the transmission means is coupled to the operating means via a linkage system for transmission of torsional movements of * 30 the operating means to steering movements of at least one rear wheel independently of pivotal movements of the opera- ' ting means. Further developments of the steering device according to the 35 invention are disclosed in the subclaims. The invention will be described in more detail below with reference to the accompanying drawings, which illustrate schematically different embodiments of the steering device according to the invention and in which fig 1 is a perspective view of a steering device for a transport vehicle according to a first embodiment, where all the wheels are directly actuated by an operating means, fig 2 is a perspective view of a steering device according to a second embodiment, where one front wheel and one rear wheel are directly actuated by the opera¬ ting means and the other wheels are actuated by the movement of the vehicle, fig 3 is a side view of a linkage system between the ope¬ rating means and the transport vehicle according to fig 1 or fig 2, and fig 4 is a view from above of the linkage system according to fig 3. Fig 1 shows a steering device for a transport vehicle 1 with two front wheels 2, 3 and two rear wheels 4, 5, which can be steered about steering axes 6 under the influence of a front tie rod 7 and a rear tie rod 8. Of the transport vehicle 1 itself there is only shown a front axle 9 and a rear axle 10 and a boom 11 connecting the front axle 9 to the rear axle 10. The transport vehicle 1 is steered with an operating means 12, which is pivotable in various directions. The operating means 12 consists of a pull bar 13 which is used to move the vehicle 1, and an inner bar 14, in the outer end of which there is mounted a pulling and steering handle 15. The inner bar 14 is rotatably mounted in the pull bar 13 and is secured against movements in the longitudinal direction of the pull bar 13. The pull bar 13 is articulated at its inner end to the front axle 9 or to another portion of the transport vehicle 1 via a linkage system 16, and, spaced from the front axle 9, the front tie rods 7 are articulated to an outer steering portion 17 of the linkage system 16. This means that a pivot movement of the operating means 12 about its inner end within the sector indicated by the arrows C-D will turn the front wheels 2, 3 about their steering axes 6. The pivot movement of the operating means 12 takes place in a plane which is essential- ly parallel to the surface on which the vehicle 1 is placed. A torsional movement of the inner bar 14 in the operating means 12 about its longitudinal axis actuates the turning movement of the rear wheels 4, 5 about their steering axes 6 via the linkage system 16 and a transmission means 18, in the form of a rotatable shaft 19, which is rotatably mounted in the boom 11 in order to transmit torsional movement imparted by the steering handle 15. Said torsional movements are con¬ verted with the aid of an arm 20 fixed to the rotatable shaft 19 into steering movements of the rear tie rod 8. The trans¬ mission means 18 can, for example, also consist of a steering wire, with or without a jacket, which, however, is not shown in the figures. Figs 3 and 4 show the linkage system 16 between the operating means 12 and the vehicle 1, the linkage system transmitting torsional movement from the pulling and steering handle 15 to the transmission means 18 via a first universal joint 21 and a second universal joint 22, which are coupled to each other via an inner steering portion 23, which is rotatably mounted in the outer steering portion 17. The universal joints 21, 22 can consist of simple knuckle joints. Simple knuckle joints have, however, the disadvantage that the angle between the shafts for transmission of the torsional movements, is limit- ed to the approximate interval between -45 degrees and +45 degrees. In certain embodiments of the vehicle, a pivot angle within this interval between the operating means 12 and the vehicle should be sufficient. In other embodiments of the vehicle, it is desirable that the operating means 12 be able to be pivoted to an angle of 90 degrees between the operating means 12 and the vehicle 1. This requires that the first uni¬ versal joint 21 consist of a conical gear transmission or double knuckle joints, which can transmit torsional movements in the interval between -90 degrees and +90 degrees. The outer steering portion 17, at its end facing the vehicle, is mounted in a first bearing means 24 for pivot movements in the sector indicated by the arrows C-D in figs 1 and 2. An- other bearing means 25 is arranged at the other end of the outer steering portion 17, said bearing means permitting pivot movements of the operating means 12 in the sector indi¬ cated by the arrows E-F, essentially perpendicular to the plane of the supporting surface. In another embodiment of the steering device of the transport vehicle 1, which is shown in fig 2, the steering of one front wheel 2 and one rear wheel 4 is effected directly by the operating means 12 via the front tie rod 7 and a rear tie rod 8, while the steering of the other wheels 3, 5 is effected by the movement of the vehicle by virtue of the fact that said wheels have a so-called castor suspension, which permits the wheels to follow the direction determined by the vehicle. Such an arrangement provides significantly lower steering friction forces, and this makes the vehicle easier to maneuv¬ er, especially when it is heavily loaded. The steering angle of the rear wheels can be locked by a blocking device 26, which is disposed on the operating means 12 and which engages the inner bar 14 and locks it against torsional movements. The length of the vehicle can also be changed due to the fact that the boom 11 is constructed so that its length can be varied, the rotatable shaft 19 being constructed in a corre¬ sponding manner. The change in length is made possible, for example, by virtue of the fact that the boom 11 and the rota¬ table shaft 19 are telescopically arranged. If desired, the vehicle can also be equipped with a simple auxiliary motor to facilitate pulling and maneuvering of the vehicle. The vehicle can also be provided with a pulling device so that it can be pulled behind and be operated from a tractor.

Claims: Claims 1. Steering device for a transport vehicle (1) with at least one front wheel (2,3) and at least one rear wheel (4,5), each wheel being suspended for turning about a steering axis (6) , essentially perpendicular to the supporting surface on which the wheels (2,3,4,5) are intended to roll, at least one of the front wheels (2,3) being coupled via a front tie rod (7) to an operating means (12) in such a manner that pivot move¬ ments of the operating means (12) in a plane are transmitted via the front tie rod (7) to steering movements of the front wheel (2,3), at least one of the rear wheels (4,5) being coupled via a rear tie rod (8) to a transmission means (18), disposed to be actuated by movements of the operating means (12) to effect steering movements of the rear wheel (4,5), c h a r a c t e r i z e d in that the transmission means (18) is coupled to the operating means (12) in a linkage system (16) for transmission of torsional movements of the operating means (12) to steering movements of at least one rear wheel (4,5) independently of pivotal movements of the operating means (12) . 2. Steering device according to Claim 1, c h a r a c t e r¬ i z e d in that the pivot movement of the operating means (12) takes place in a plane (C-D) which is essentially paral¬ lel to the supporting surface, and that the torsional move- ments (A-B) of the operating means (12) take place about its longitudinal axis. 3. Steering device according to Claim 1 or 2, c h a r a c ¬ t e r i z e d in that the transmission means (18) comprises a shaft (19) which is rotatable in the longitudinal direction of the vehicle, on which said shaft and arm (20) are mounted. 4. Steering device according to one or more of Claims 1 - 3, c h a r a c t e r i z e d in that the operating means (12) comprises a pull bar (13), in which an inner bar (14) is rotatably mounted and is joined to the transmission means (18) via the linkage system (16). 5. Steering device according to one or more of Claims 1 - 4, c h a r a c t e r i z e d in that the linkage system (16) comprises a first universal joint (21) and a second universal joint (22), which are coupled to each other via an inner steering portion (23), which is rotatably mounted in an outer steering portion (17), said outer steering portion (17) having at one end a first bearing means (24), which is jour- nalled in the transport vehicle (1), and at its other end has a second bearing means (25), in which the operating means (12) is journalled. 6. Steering device according to one or more of Claims 1 - 5, c h a r a c t e r i z e d in that a blocking device (26), disposed on the operating device (12) , can engage the inner bar (14) and lock it against torsional movements. 7. Steering device according to one of Claims 1 - 6, c h a ¬ r a c t e r i z e d in that the transmission means (18) and a boom (11), joining a front axle (9) and a rear axle (10) of the transport vehicle (1), are telescopically arranged so that the distance between the front (2,3) and rear wheels (4,5) can be changed.

Inventors: OESTLING JAN-ERIK, OESTLING, JAN-ERIK
Applicants: OESTLING JAN ERIK, OESTLING, JAN-ERIK
Application year: 1993
Main classification: B62B3
IPC codes: B62B3