GB2042998A - Steering mechanism for articulated vehicles - Google Patents

Abstract

A steering mechanism for an articulated vehicle having first and second frame sections with one of the frame sections having a pair of idler links 58 and 60 pivotally mounted thereto by laterally spaced pivot pins 62, 64 and the other frame section 12 having a pair of drive links 50 and 52 pivotally connected thereto by laterally spaced pivot pins 54, 56. The free ends of adjacent driver and idler links on each side of the vehicle are pivotally interconnected by pivot pins 46, 48 and operatively associated with a steering jack 38, 40 which, upon expansion and contraction, serves to provide relative movement of the first and second frame sections about a vertical steer axis "A". The pivot pins 62, 64 are spaced apart by an amount which is substantially equal to the distance between the pivot pins 62, 64 and the pivot pins 46, 48, and the pivot pins 54, 56 are spaced apart by an amount which is substantially equal to one half of the distance between the pivot pins 54, 56 and the pivot pins 46, 48. <IMAGE>

Description

SPECIFICATION Steering mechanisms for articulated vehicles This invention reiates to steering mechanisms for articulated vehicles.

The invention has particular application to selfpropelled scraper vehicles of the type comprising a tractor-drawn scraper bowl in which the tractor and scraper are pivotally interconnected about a vertical steering axis.

Our United States Patent 3,292,724 (Fryer) discloses a steering and coupling mechanism for an articulated vehicle having relatively movable first and second frame sections that are interconnected about a vertical steer axis and have incorporated therewith power-operated means that act through a pair of V-shaped drive links and a pair of V-shaped idler links for moving one frame section relative to the other. The drive and idler links are identical in configuration and are so arranged that when the frame sections are aligned for straight-ahead movement, the pivot connections between the links and the frame sections are located along the longitudinal centre axis of the vehicle and the pivot connections between the links are located along a line that is normal to the longitudinal centre axis and passes through the steer axis.

By the present invention there is provided a steering mechanism for an articulated vehicle comprising first and second frame sections, means pivotally interconnecting the frame sections about a steering axis for relative steering articulation therebetween to either side of straight-ahead steering alignment of the frame sections, a pair of drive links and a pair of idler links, means connecting one end of one of the idler links and one end of the other of the idler links to the second frame section for pivotal movement about laterally spaced first and second pivot axes located on opposite sides of the longitudinal centre axis of the vehicle when the frame sections are in straight-ahead steering alignment, means connecting one end of one of the drive links and one end of the other of the drive links to the first frame section for pivotal movement about laterally spaced third and fourth pivot axes located on opposite sides of the longitudinal centre axis, means connecting the other ends of the idler links and the other ends of the drive links for relative pivotal movement about fifth and sixth pivot axes, a pair of fluid pressure-operated steering jacks located on opposite sides of the longitudinal centre axis with one end of the steering jacks pivotally connected to the drive and idler links at the fifth and sixth pivot axes respectively and the other ends of the steering jacks pivotally connected to the second frame section, the pivot axes being so located that the distance between the first and second pivot axes is substantially equal to the distance between the first and fifth pivot axes or between the second and sixth pivot axes, whereas the distance between the third and fourth pivot axes is substantially equal to one-half the distance between the third and fifth pivot axes or between the fourth and sixth pivot axes.

The present invention is thus directed to a steering mechanism that is generally similar to the previously described type, but is an improvement thereover inasmuch as it employs links members that have the lengths thereof and the pivot connections associated therewith so arranged that a flatter torque curve is realized during turning manoeuvres. As a result, more efficient steering is provided, with increased torque being available when the tractor is returning from a turned position to a straight-ahead aligned position.

In the accompanying drawings: Figure 1 is an elevational view showing an articulated scraper vehicle employing one embodiment of a steering mechanism in accordance with the present invention; Figure 2 is an enlarged view showing in detail the steering mechanism employed with the vehicle of Figure 1; Figure 3 is a fragmentary front view of the steering mechanism on the line 3-3 of Figure 2, in the direction of the arrows; Figure 4 is a fragmentary plan on the line 21 4 of Figure 3, in the direction of the arrows; and Figure 5 is a fragmentary plan similar to Figure 4 but showing the relative positions of the various components of the steering mechanism when the tractor is in a full turn relative to the scraper bowl.

Figure 1 of the drawings shows an articulated scraper vehicle comprising a two-wheeled overhung tractor 1 2 which is connected to a trailing scraper bowl 14 by a steering mechanism 16 that is shown in detail in Figures 2 to 5. The steering mechanism is combined with a vertically upstanding frame member 1 8 the lower portion of which is pivotally connected to the tractor 12 for oscillatory movement about a horizontal axis by pivot connections 20 and 22. A gooseneck (draw bar) 24 has a pivot housing 26 formed therewith that is journalied on a king pin (not shown) fixed to the lower portion of the frame member 1 8 for rotation about a vertical steer axis "A" between the tractor and the scraper bowl.Similarly, as is seen in Figures 2 and 4, the upper portions of the frame member 18 and the draw bar 24 are rigidly formed with pivot housings 28 and 30 which are interconnected by a pin 32, the longitudinal centre axis of which is coincidental with the steer axis "A".

As is usual with scrapers of the type seen in Figure 1 , the draw bar 24 is rigidly connected to a pair of transversely spaced pull arms 34, only one of which is shown, that extend rearwardly for pivotal connection with the scraper bowl 14. In addition, the scraper includes the usual operating mechanism generally indicated by the reference numeral 36 for the purpose of raising and lowering the scraper bowl 14 and the usual apron associated therewith.

As is best seen in Figure 3, the steering mechanism 1 6 includes a pair of double-acting hydraulic jacks 38 and 40, each of which incorporates the usual relatively reciprocable piston rod and cylinder members. In this instance, the cylinder members of the respective jacks are pivotally connected by vertically extending pins 42 and 44 to brackets rigidly secured to opposite sides of the draw bar 24, and the piston rods are pivotally connected by vertically extending pins 46 and 48 to identical drive links 50 and 52. The drive links 50 and 52 are themselves pivotally connected by vertically extending pins 54 and 56 to the frame 1 8 forwardly of the pivot housing 27.

A pair of identical idler links 58 and 60 are pivotally connected to the drive links at 46, and 48, and extend rearwardly for pivotal connection to the draw bar 24 by way of vertically extending pins 62 and 64.

As is seen in Figures 2 and 3, the drive links 50 and 52 have duplicate members 50' and 52' respectively positioned below them and pivotally connected to the pins 46 and 48, and 54 and 56.

Similarly, the idler links 58 and 60 have duplicate members 58' and 60' respectively positioned below them and pivotally connected to the pins 46 and 48, and 62 and 64.

As is conventional in operating mechanisms of the above-described type, the jacks 38 and 40 are connected to a fluid operating system (not shown) which selectively provides pressurized fluid to the opposite ends of the jacks. Thereby, when pressurized fluid is directed to the cylinder end of the jack 40 and the rod end of the jack 38, the steer linkage causes the tractor 1 2 to be rotated counterclockwiese about the steer axis "A" relative to the scraper bowl 14 so that the drive and idler links assume the relative positions shown in Figure 5. Conversely, when pressurized fluid is directed to the opposite ends of the respective jacks, the steer linkage will cause the tractor 1 2 to be rotated clockwise about the steer axis "A" relative to the scraper bowl 14.

It will be noted with referecne to Figure 4 that when the tractor 12 and the scraper bowl 14 are in longitudinal alignment so that the vehicle is moving straight ahead, the centres of the pivot connections defined by the pins 54 and 56 are equally spaced from the longitudinal centre axis "B" of the vehicle, and likewise the centres of the pivot connections defined by the pins 62 and 64 are equally spaced from the longitudinal centre axis "B". Further, in this straightahead condition the centres of the pivot connections defined by the pins 46 and 48, and the steer axis "A", are located along an axis "C" which is perpendicular to the longitudinal centres axis "B" of the vehicle.Also, the distance between the centres of the pins 62 and 64 is substantially the same as the distance between the centres of the pins 46 and 62 or between the centres of the pins 48 and 64, whereas the distance between the centres of the pins 54 and 56 is substantially one-half the distance between the centre of the pins 48 and 56 or between the centres of the pins 46 and 54. In addition (stili considering the vehicle in the straight-ahead position shown in Figure 4), a straight line passing through the centres of the pivot connections defined by the pivot pins 56 and 64 and a straight line passing through the centres of the pivot connections defined by the pivot pins 54 and 62 will intersect at a point "D" located on the longitudinal centre axis "B".

This particular arrangement of links and pivot connections provides improved steering torque characteristics, with a simple and rugged steering mechanism which is relatively inexpensive to manufacture, assembly and service.

Claims (4)

1. A steering mechanism for an articulated vehicle comprising first and second frame sections, means pivotally interconnecting the frame sections about a steering axis for relative steering articulation therebetween to either side of straight-ahead steering alignment of the frame sections, a pair of drive links and a pair of idler links, means connecting one end of one of the idler links and one end of the other of the idler links to the second frame section for pivotal movement about laterally spaced first and second pivot axes located on opposite sides of the longitudinal centre axis of the vehicle when the frame sections are in straight-ahead steering alignment, means connecting one end of one of the drive links and one end of the other of the drive links to the first frame section for pivotal movement about laterally spaced thrid and fourth pivot axes located on opposite sides of the longitudinal centre axis, means connecting the other ends of the idler links and the other ends of the drive links for relative pivotal movement about fifth and sixth pivot axes, a pair of fluid pressureoperated steering jacks located on opposite sides of the longitudinal centre axis with one end of the steering jacks pivotally connected to the drive and idler links at the fifth and sixth pivot axes respectively and the other end of the steering jacks pivotally connected to the second frame section, the pivot axes being so located that the distance between the first and second pivot axes if substantially equal to the distance between the first and fifth pivot axes or between the second and sixth pivot axes, whereas the distance between the third and fourth pivot axes is substantially equal to one-half the distance between the third and fifth pivot axes or between the fourth and sixth pivot axes.

2. A steering mechanism according to claim 1, in which the first and second frame sections are pivotally interconnected about a vertical steering axis for the relative steering articulation therebetween, the pair of drive links comprise identical straight links, and the pair of idler links comprise identical straight links.

3. A steering mechanism according to claim 1, in which the first and second frame sections comprise a tractor and a trailing bowl respectively of an articulated scraper vehicle having the tractor and trailing bowl pivotally interconnected about a vertical steering axis, the pair of drive links comprise identical straight links, the pair of idler links comprise identical straight links, and the steering jacks comprise a pair of double-acting fluid pressure-operated steering jacks located on opposite sides of the longitudinal axis with the rod ends of the steering jacks pivotally connected to the drive and idler links at the fifth and sixth pivot axes respectively and the cylinder ends of the steering jacks pivotally connected to the trailing bowl.

4. A steering mechanism for an articulated vehicle comprising first and second frame sections, substantially as hereinbefore particularly described and as shown in the accompanying drawings.