GB2171368A

GB2171368A - Single steerable wheel suspension

Info

Publication number: GB2171368A
Application number: GB08602731A
Authority: GB
Inventors: Terry Neil Trebilcock
Original assignee: FMC Corp
Current assignee: FMC Corp
Priority date: 1985-02-22
Filing date: 1986-02-04
Publication date: 1986-08-28
Also published as: FR2577855A1; BE904265A; IT8619365A0; DE3601820A1; NL8503505A; AU5218986A; JPS61193905A; GB8602731D0

Abstract

A sprung suspension system (10) for a single steerable wheel (76) of a three wheeled sweeper (11) is disclosed which includes wheel supporting elongated swing arms (40) pivoted to a fork assembly (12) about a substantially horizontal axis with springs (52) connected between the rear end of each swing arm and the fork assembly; the swing arms are rigidly secured together at their forward ends by means (90) to prevent independent pivotal movement of the arms relative to each other, thereby maintaining the rolling plane of the wheel substantially normal to the horizontal axis of the fork assembly and thus greatly minimizing tire wear when making sharp turns or driving along rough roads. <IMAGE>

Description

SPECIFICATION Single wheel suspension system The present invention pertains to vehicle suspension systems and more particularly relates to a suspension system for a sprung single steerable wheel of a sweeper or the like.

Three wheel sweepers with a single steerable front wheel of the type disclosed in United States Patent No.4457044 and assigned to the applicants are well known. However, the single front wheel of this Erdman et al vehicle is an unsprung wheel.

A single steerable front wheel suspension system is known and is similar to the Erdman et al suspension system except that the single wheel is rotatably supported on swing arms that are independently journaled on opposite sides of a fork assembly which is supported by the vehicle chassis for steering movement about a vertical axis. One end of a pair of leaf springs are secured to the associated swing arms while the other ends of the springs are movably connected to the fork assembly by links. A pair of shock absorbers are also connected between the associated swing arms and the fork assembly.

However, this prior art suspension system proved to be unsatisfactory due to excessive wheel wobble which resulted in excessive tire wear.

According to the present invention, a sprung, single steerable wheel suspension system for a vehicle comprises a fork assembly pivoted to the vehicle chassis and supporting a pair of spaced swing arms to which the wheel is journaled, the swing arms being rigidly connected together to prevent independent movement of the arms and thus minimise wheel tire wear.

The invention is illustrated, byway of example in the Drawings, wherein: Figure 1 is a perspective illustrating a street sweeper incorporating a resiliently spring front wheel suspension system in accordance with the present invention; Figure 2 is a side elevation of the suspension system of Figure 1, removed from the sweeper; Figure 3 is a front elevation of the suspension system with portions of the swing arms cut away; Figure 4 is a horizontal section taken along lines 4-4 of Figure 2; and Figure 5 is an exploded perspective of the suspension system with the wheel and certain components of the right side being omitted.

The resiliently sprung, single front wheel suspension system 10 shown in the Drawings is intended for use in a heavy vehicle such as a street sweeper 11 of the type disclosed in the aforementioned United States Patent No.4457044; which is incorporated by reference herein.

As the components on the right and left sides of the suspension system 10 are identical, the same numerals will be used to identify right and left components.

The suspension system 10 comprises a fork assembly 12 which includes an upright spindle 14 that is rotatably received in the chassis 15 of the vehicle 11 and is operatively connected to the steering wheel of the vehicle by means not shown.

The fork assembly 12 (Figures 2-5) includes rigid legs 16 which project downwardly and forwardly of the spindle 14 and are reinforced by flanged side plates 18 and straps 20 or the like. The legs 16, reinforcing plates 18 and straps 20 are welded together and to an upper structure 22. The upper structure includes a thick central portion 24, to which the spindle 14 is welded, a front plate 26 and a rear plate 28 which includes a downwardly bent portion 29. A pair of generally triangular boxes 30 (only one being shown) are welded to the associated plates 18 and have spaced ears 31 projecting downwardly therefrom to cooperate with sleeves 32 to define spring mounts 33. Shock absorber mounts 34 and swing arm pivot pins 36 are also secured to the fork assembly.

Right and left swing arms 40 include bores 42 (Figure 5) intermediate their ends which have bushings 44 fitted therein for pivotally receiving the associated pivot pins 36. Thrust washers 45 are disposed around the pivot pins 36 and between the associated arms 40 and legs 16 of the fork assembly 12. The rear end portion of each swing arm has a spring supporting pad 46 welded thereto which cooperates with a spring clamp pad 48 and connectors 50 such as cap screws or bolts to rigidly clamp one end of an associated leaf spring 52 to the associated arm 40. The other end of each leaf spring is swingably connected to the associated spring mounts 33 (Figures 4 and 5) of the fork assembly 12 by a pair of split end links 54, a pair of bushings 56, a pair of shafts 58 and a pair of bolts 60 (only one being shown) which clamp the split end links on the shafts 58.

A pair of shock absorbers 64 are provided with one end of each shock absorber pivotally connected to the associated shock absorber mount 34 by a bushing 66 and a cap bolt 68. The other end of each shock absorber is pivotally connected to ears 70, welded to the associated spring clamp pad 48, by a bolt 72.

A conventional wheel 76 (Figure 1) and its pneumatic tire are rotatably mounted on a shaft 80 having flats 82 near each end thereof. The shaft 80 is received in slots 84 in each swing arm 40 and is clamped in position by straps 86 and cap screws 88 with the flats 82 in the shaft preventing rotation of the shaft 80.

It will be understood that the fork assembly 12 defines an unsprung portion of the suspension system 10; while the swing arms 40, springs 52, and shock absorbers 64 define the sprung portion of the suspension system.

An important feature of the invention is that the forward end portions of the swing arm extend forwardly of the wheel 76 and are rigidly connected together by tie plate 90. Cap screws 92 are indicated as the preferred connecting means.

In operation, as the street sweeper 11 is driven along a road at speeds as high as thirty miles per hour, the springs 52 and shock absorbers 64 cooperate to provide for a smooth ride. When the heavy sweeper 11 is turned to the right or to the left, or when the wheel 76 rides on a surface that is not level transversely of the direction of movement of the vehicle, the tie plate 90 assures that both swing arms 40 will pivot about the pivot pins 36 in unison thus maintaining the upright rolling plane of the wheel 76 and the upright planes of the swing arms parallel at all times.Stated in another way, if the tie plate 90 was removed and the heavy sweeper was turned sharply to the right during operation, the rear end of the right swing arm would raise and the rear end of the left swing arm would lower thus tilting the rolling plane of the wheel relative to the upright planes of the swing arms. Conversely, if the sweeper was turned to the left, the rear end of the left swing arm would raise.

It has been determined by the use of a sweeper without a tie plate 90 that tire wear is so extreme that the tire becomes bald after only about 500 miles of use when the swing arms are not tied together. It will also be apparent that driving of the sweeper along a linear path over rough roads which vary in inclination transversely of the direction of travel of the vehicle will cause the swing arms to pivot relative to each other causing scuffing and undue wear of the tire 78 if the two swing arms are not tied together by the tie plate 90.

The tie plate 90 acts to rigidly connect the swing arms together for equal and simultaneous pivotal movement about their pivot axis, enabling the springs and shock absorbers connected between the swing arms and the fork assembly to maintain the rolling plane of the wheel substantially normal to the wheel supporting surface.

Claims

1. A sprung, single steerable wheel suspension system for a vehicle comprising a fork assembly pivoted to the vehicle chassis and supporting a pair of spaced swing arms to which the wheel is journaled, the swing arms being rigidly connected together to prevent independent movement of the arms and thus minimise wheel tire wear.

2. A suspension system as claimed in Claim 1, wherein: the spaced swing arms are elongate and have first and second end portions and are supported, intermediate the end portions, to the fork assembly for pivotal movement about a horizontal axis; an axle is secured to the swing arms; the tired wheel is journaled on the axle; first spring means are operatively connected between one of the swing arms and the fork assembly; and second spring means are operatively connected between the other swing arm and the fork assembly; means rigidly connecting the swing arms together thereby to ensure that both swing arms will pivot equal amounts about said horizontal axis.

3. A suspension system as claimed in Claim 2, wherein the connecting means is a tie plate which is removably connected to the corresponding end portion of each swing arm.

4. A suspension system as claimed in Claim 2 or Claim 3, wherein the spring means are leaf springs with one end of the first leaf spring connected to the first end portion of one of the swing arms and one end of the second leaf spring connected to the first end portion of the other swing arm; the connecting means being rigidly connected to the second end portions of the swing arms.

5. A suspension system as claimed in Claims 3 and 4 and for the front wheel of a vehicle, wherein: the fork assembly has spaced, downwardly extending legs; the pair of swing arms have forward and rear end portions; means are provided to pivotally connect each of the swing arms to an associated one of the spaced legs near to the centre ofthe swing arms for pivotal movement about said horizontal axis; the axle is secured to the swing arms near the rear endsthereof; the first leaf spring is operatively connected to the rear end of one of the swing arms; the second leaf spring is operatively connected to the rear end of the other swing arm; and the connecting means rigidly connect the forward ends of the swing arms together.

6. A suspension system as claimed in any of Claims 1 to 5, wherein shock absorbers are operatively connected between the swing arms and the fork assembly.

7. A resiliently sprung, single steerable wheel suspension system for a vehicle substantially as described with reference to or as shown by the Drawings.