GB2082986A

GB2082986A - Variable Track Width Steering Systems

Info

Publication number: GB2082986A
Application number: GB8125191A
Authority: GB
Original assignee: Coles Cranes Ltd
Current assignee: Coles Cranes Ltd
Priority date: 1980-09-03
Filing date: 1981-08-18
Publication date: 1982-03-17
Also published as: GB2082986B

Abstract

In a mobile crane or aerial lift platform vehicle wherein at least one of the axles is extendable and wherein a tubular housing 14 carries telescopically adjustable axle beams 16, a steering actuator 26 is carried on at least one of the beams and is connected to a steering link 36 connected between the wheel and the outer end of the beam. The arrangement is such that the distance between the actuator and the steering ink is not altered by extension or contraction of the beam relative to its housing. <IMAGE>

Description

SPECIFICATION Mobile Cranes or Aerial Lift Platforms This invention relates to aerial lift platforms or cranes mounted on a mobile chassis and carrying an extendable boom.

The increasing demand for machines with greater outreach throughout 3600 rotation, has resulted in the use of extending axles or outriggers (depending on the requirement for fully mobile or fixed base operation) to improve the stability base when the rotating upper structure is normal to the longitudinal axis of the chassis.

This had led to a problem with the steering linkage on the chassis base which has not heretofore been resolved efficiently and safely.

It is recognised with both aerial lifting platforms and cranes that when a boom on the rotating upper structure is in a position at 900 to the chassis longitudinal axis, that the overturning moment of the boom together with the load lifted on the crane, or on the boom plus basket for lift platforms, reaches a maximum value because of the relative width to length of the chassis base.

Previously, improvement in operation over the side of the chassis has been achieved by the use of extending axles or extending outriggers. When it is necessary to achieve full mobility of the machine for all positions of the boom, then extending axles have been used for the purpose.

To utilise extending axles efficiently, the steering geometry and linkage must compensate for the change in position of the wheels owing to the axle extension.

Previously this has been achieved with the use of a large number of components and consequently some of the bracketry has been positioned forward of the axle in a vulnerable position which could affect the safety of the machine.

Steering linkage which may be telescopic is normally held in position, at its minimum and maximum extension, by pins located at suitable positions in the drag rods.

A vehicle in accordance with this invention carrying a boom or jib for a crane or aerial lifting platform, has extendible axle(s) comprising a cylindrical housing carrying extendible axle beams one at each side, a steering actuator, e.g. a hydraulic piston cylinder, being carried on at least one of the beams with its mounting bracket preferably extending out through a slot in the wall of the housing, the cylinder (or piston) being thus pivotally connected between the steering link and beam so its position is not altered by extension or contraction of the beam relative to the housing.

This means that the only adjustment, other than actuation of the ram to drive the axle beams "in" and/or "out", is the pinning of the track rod in the contracted or extended position resulting in a very much easier adjustment than has hitherto been possible.

The invention will now be further described by way of example, with reference to the accompanying drawings in which: Figure 1 is a front view of one embodiment of a mobile lift or access platform vehicle in accordance with the invention, and Figure 2 is a sectional view to an enlarged scale of the front axle of the vehicle shown in Figure 1.

Referring to Figure 1 , the vehicle comprises a chassis generally indicated at 2 mounted on front wheels 4 and rear wheels 6. The rear wheels are driven to drive the vehicle.

A platform 8 is pivotally mounted on the chassis and carries a telescopically extensible boom 10 which itself carries an access platform 12 at its outer end.

The front extending axle shown in detail in Figure 2 comprises a cylindrical or rectangular section housing 14 carried by the main chassis 2 of the vehicle and carrying two axle beams 1 6 and 18, one at each side and each of which carries a wheel 4.

The two beams 1 6 and 1 8 are driven out from and into the cylindrical housing by a double acting hydraulic ram 20 located between the beams and pivotally connected thereto at 22 and 24.

A hydraulic steering actuator 26 is pivotally connected to the beam 1 6 through a bracket 28 which extends out through a slot 30 in the wall of the housing cylinder 14. Thus as the beam 16 is extended longitudinally out from the cylinder 1 4.

the actuator is also moved longitudinally for an equal distance.

The actuator cylinder is pivotted at 32 to the bracket 28, and the actuator piston 34 is pivotted at 36 to one end of one arm of a double arm steering link 38 pivotted at 40 to the outer end of the beam 1 6 and carrying the stub axle (not shown) of the wheel 4.

The end of the other arm of the link 38 is pivotted at 42 to one end of a telescopically extensible track rod 44 mounted on the other side of the axle housing from the actuator.

Thus when the beams are extended the only operation which needs to be carried out is the pinning of the track rod in its extended position and equally on subsequent retraction, pinning the track rod in its retracted position. This is done by a removable pin 46 passing through one of two appropriately positioned holes 48 in the two parts of the telescopic track rod.

The right hand front wheel 4 is carried on a single arm bracket 50 carried at the end of the beam 1 8. The outer end of the arm of the bracket is pivotally connected at 52 to the other end of the telescopic track rod 44 so that as the hydraulic actuator 1 6 operates to turn the left hand front wheel the right hand front wheel is turned through an equal angle by the track rod.

The rear axle of the vehicle (not shown in detail) is not steerable. It is however extensible and comprises two beams each carrying a wheel and each telescopically mounted in a housing in a similar manner to the beams 14, 1 6 of the front axle. The rear beams are driven out and into their housing by a hydraulic ram similar to the ram 20 acting on the front beams. When the front and rear axles are in their extended or retracted positions, a microswitch operates to sense the position and operates to stop the hydraulic drive.

Locking pins may be provided to pin the axles in their extended and/or retracted position.

Unless the microswitchs indicate that the axles are extended, the boom and lift angles will be limited.

When it is desired to extend the axles to stabilise the vehicle from its running "axle retracted" position, the vehicle is located in a position where there is room to move safely in each direction for about 5 metres and with a clearance of about 1 metre on each side. The hydraulic rams 20 are then pressurised to extend one axle and the vehicle is moved in the safe direction. One wheel will then creep out followed by the other. The direction of travel of the vehicle may be changed during axle extension. Once one axle is extended and locked the procedure may be repeated for the other axle.

The actuator is mounted within the confine of the chassis and so is liable to be damaged.

Claims

1. A mobile crane or aerial lift platform wherein at least one of the axles comprises a cylindrical housing carrying an extendible beam at each side of the beam carrying a wheel at its outer end, a steering actuator being carried on at least one of the beams and being connected to a steering link connected between the wheel and the outer end of said beam, the arrangement being such that the distance between the actuator and the steering link is not altered by extension or contraction of the beam relative to its housing.

2. A vehicle as claimed in Claim 1 wherein the steering actuator comprises a hydraulic cylinder and piston, the piston (or cylinder) being carried on a mounting bracket extending out from the beam through a slot in the side of the cylindrical housing, the cylinder (or piston) respectively being pivotally connected to one end of the steering link.

3. A vehicle as claimed in either Claim 1 or 2 wherein the track rod extends alongside the axle on the other side of the axle from the hydraulic actuator and between the other arm of the said steering link and an arm of a steering link for the other wheel carried at the outer end of the other extendible beam of the axle.

4. A vehicle as claimed in Claim 3 wherein the track rod is formed of telescopically engaged members which may be pinned together both when contracted and/or when extended.

5. A vehicle as claimed in any of the preceding Claims wherein the beams are driven out from and into their cylindrical housing by means of a double acting cylindrical ram positioned within the beams and pivotally connected thereto.

6. An extendible axle assembly for a vehicle as claimed in any one of the preceding claims.

7. An extendible axle assembly substantially as hereinbefore described with reference to Figure 2 of the accompanying drawings.

8. An aerial lift platform substantially as hereinbefore described with reference to the accompanying drawings.