FORM-2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
RACEWAY BASED STEERING ACTUATION AND
LINKAGE MECHANISM FOR STEERING OF
MULTI-AXLE SEMI-TRAILER
DIRECTOR GENERAL,
DEFENCE RESEARCH AND
DEVELOPMENT ORGANIZATION (DRDO)
an Indian National
of Ministry of Defence, Government of India,
Room No. 348, B-Wing,
DRDO Bhavan, Rajaji Marg, New Delhi-110011, India
INVENTORS:
1. CHAUDHURI SANJAY
2. SAINIVIKRAM
3. SINGH MANMOHAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

FIELD OF THE DISCLOSURE
The present disclosure relates to multi-axle articulated vehicles, which are particularly used for transporting high payloads having very large and extra-long cargo by road.
More particularly, the present disclosure relates to steering of such multi-axle articulated vehicles.
BACKGROUND
There is a substantia] increase in demand for transportation of high payloads having very large and extra-long cargo by road because of a high growth in construction, power, shipping, mining, petroleum sectors and the like. The multi-axle articulated vehicles have been found to be the most suitable means of transport for such demanding applications.
The use of multi axle articulated vehicle in the defence sector has already gained significance and today many strategic equipments and weapon systems are based on articulated vehicle for the reasons of good mobility, flexibility, short realization time etc.
However, the multi-axle articulated vehicles have their own limitations in terms of maneuverability due to a constant turning circle diameter, road widths and limited road infrastructure available. This degree of constraint will rise with the demand in transportation of very large consignments of the above industrial sectors. Improvement in the steering mechanisms of such articulated vehicles is gaining momentum due to the above needs.
The turning circle diameter (TCD) and the road width reduces for an articulated vehicle by steering of non-driven axles of a semi-trailer, which enables an articulated vehicle with steerable axles to negotiate a sharp turn better than that of non-steered axles and improves its overall mobility. It also reduces the locked-in forces and thus, reduces tyre drag and wear by achieving a free rolling condition.

The steering systems for articulated vehicles also have their own limitations as the limit of steering is not known, which requires skilled drivers or otherwise requires steering systems in which the working limits are defined. The merit of effective steering of articulated vehicles goes beyond any doubt.
The relationship between the articulation angle of prime mover and thereby, the differential strokes generated in actuation cylinders is the most important factor for efficient steering of a semi-trailer. An effective steering is obtained when semi-trailer wheel stations are steered with respect to articulation angle up to a certain limit along with predetermined articulation angle v/s actuation cylinder stroke characteristic.
The prior art mechanisms do not bring out any such information for the requirement of efficient steering of a semi-trailer. The prior art mechanisms normally used bell cranks with suitable elliptical cutouts in operative association with the fifth wheel.
Many prior art mechanisms generate an output signal, which fails to impose an actual angle of incidence in steerable axles, which sufficiently approximates a theoretical angle of incidence in a desired range of relative angels between the towing vehicle and the steerable semi-trailer.
The extent of difference between the actual angle of incidence and the theoretical angle of incidence of a steerable axle will therefore vary according to the type of steering mechanism chosen and will be very much dependent upon the characteristics between the fifth wheel rotation and the differential strokes generated in hydraulic cylinders due to this.
Moreover, many prior mechanisms discuss about the steering of one or two axles of semi-trailers which are suitable for short & light payload semi-trailers and the wheel station rotates only in one direction for a particular turning.
With an increase in the number of axles, and particularly, for a semi-trailer with hydraulic gooseneck structure, the instantaneous centre of rotation of a semi-trailer falls between the axle rows and hence, the direction of rotation of the wheels on

either side of the instantaneous centre become opposite and therefore, require complex steering linkage.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
It is an object of the present disclosure to provide a raceway based steering actuation system for governing the limits of articulation.
ft is another object of the present disclosure to provide a raceway based steering actuation mechanism for steering of one or two axles of a semi-trailer which is suitable for high payloads to be carried by road.
It is still another object of the present disclosure to provide a raceway based steering actuation mechanism for steering of a semi-trailer which is suitable for very large payloads to be carried by road.
It is yet another object of the present disclosure to provide a raceway based steering actuation mechanism for steering of a semi-trailer which is suitable for extra-long payloads to be carried by road.
It is yet another object of the present disclosure to provide a raceway based steering actuation mechanism by which the desired stroke-articulation angle characteristics can be obtained.
It is yet another object of the present disclosure to provide a raceway based steering actuation mechanism, in which the structural strength of the semi-trailer need not be compromised.
Other objects and advantages of the present disclosure will be more apparent from the following description when read in conjunction with the accompanying figures, which are not intended to limit the scope of the present disclosure.

SUMMARY
In accordance with the present disclosure, there is provided a steering actuation and linkage mechanism for steering of a multi-axle semi-trailer which is coupled to the fifth wheel coupler of the prime mover and steerable wheel stations of the multi-axle semi-trailer unit, the steering actuation mechanism comprises:
a drive shaft housing having an extended platform, coupled to a drive shaft provided with side rollers, the drive shaft housing rigidly attached to a turn-table fitted with a steering wedge and rotating on the fifth wheel coupler;
the drive shaft coupled to be slidable inside the drive shaft housing without rotating on its own axis during the operation;
side rollers assembly on the drive shaft assembled through a centre pin, the centre pin engaged with profiled raceway through a centre roller, the raceway bolted to the base plate of a semi-trailer gooseneck structure;
a butterfly housing pivoted on the gooseneck structure and incorporating a main body and cylinder mounting brackets, the butterfly housing coupled to the centre pin through the driven shaft and a plurality of hydraulic actuation cylinders; the driven shaft slidable inside the butterfly housing,
wherein the profile of the raceway is configured to control the cut-off limits of the steering actuation mechanism, in order to generate a linear relationship between the articulation angle of the prime mover and the different strokes of the hydraulic actuation cylinders.
Typically, the limited rotation of the pivoted butterfly housing and the different strokes generated in the actuation hydraulic cylinders are controlled by the centre pin and a centre roller assembly moving in the profiled raceway.
Typically, the profiled raceway is configured to define the automatic cut-off limit of the semi-trailer steering and the cut-off limit is altered by changing the profile of the raceway.

Typically, the linear relationship between the articulation angle of the prime mover and the differential strokes in the actuation hydraulic cylinders up to the cut-off limit is defined by the configuration of the profiled raceway and wherein the articulation of the prime mover beyond the cut-off limit is allowed without causing any further steering of the semi-trailer unit.
Typically, the drive shaft is supported by bushes provided on the front and rear ends of the drive shaft housing and respective oil holes provided in the middle of the bushes.
Typically, the driven shaft is supported by bushes provided in the bosses disposed at the front and rear ends of the butterfly housing.
Typically, the linkage mechanism comprises:
steering brackets mounted on all the wheel stations on each suspension unit which are interconnected by means of a plurality of tie rods;
a pivoted steering butterfly housing coupled to various steering brackets through the tie rods; and
a plurality of follower hydraulic cylinders coupled to a steering butterfly housing to receive the hydraulic actuation generated by the steering actuation mechanism and to actuate the steering linkage mechanism.
Typically, all the wheel stations of the semi-trailer unit are steered through the single steering butterfly.
Typically, the reversing of the direction of rotation of the wheel stations on either side of the instantaneous centre of rotation of the semi-trailer is enabled by the steering linkage mechanism.
Typically, the turn-table assembly comprises the drive shaft housing disposed on a base structure and a king pin flange disposed in a central aperture on the front turntable and a steering wedge bolted to the turn-table to be engaged with the fifth

wheel coupler of the prime mover.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The raceway based steering actuation mechanism for steering of a trailer in accordance with the embodiments of the disclosure present disclosure will now be explained in more detail with reference to the non-limiting accompanying drawings in which:
Figures la - Id show the schematic plan views of the raceway based steering actuation and linkage mechanisms according to the first aspect of the disclosure, which are shown in different articulated positions of the drive vehicle with reference to the centerline of the semi-trailer unit;
Figures 2a - 2b show the schematic plan views of the raceway based steering actuation and linkage mechanisms according to the second aspect of the disclosure, when the drive vehicle is driven straight ahead and when it is driven in an articulated manner respectively;
Figure 3 shows the above actuation and linkage mechanisms integrated on the tractor semi-trailer unit;
Figures 4a - 4b show the cross-sectional views of the drive shaft housing and the butterfly housing;
Figure 5 shows the cross-sectional view of the raceway based steering actuation and linkage mechanisms along a section line A-A shown in Figure 1 a;
Figure 6 shows an exploded view of the raceway based steering actuation and linkage mechanisms as per the first aspect of the disclosure;
Figure 7 shows a perspective view of the side roller assembly integrated on the drive shaft for arresting the rotation about its own axis;

Figure 8 shows the exploded perspective view of the turn-table assembly;
Figure 9 shows the characteristic of the raceway based steering actuation and linkage mechanisms in accordance with the present disclosure; and
Figure 10 shows the steering diagram of the vehicle.
DETAILED DESCRD7TION OF THE ACCOMPANYING DRAWINGS
The raceway based steering actuation and linkage mechanisms for steering of a semitrailer unit in accordance with the present disclosure will now be described with reference to the accompanying drawings, which do not limit the scope and ambit of the disclosure.
The description provided is purely by way of example and illustration. In accordance with the present disclosure, the various features and advantageous details are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein.
The examples used herein are intended merely to facilitate an understanding of the ways in which the embodiments herein may be practiced and to further enable those skilled in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The description hereinafter, of the specific embodiments of the raceway based steering actuation and linkage mechanisms for steering of a semi-trailer unit will so fully reveal the general nature of the embodiments herein that others can, by applying the current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments.

It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not for the purpose of limitation. Therefore, while the embodiments herein have been described in terms of the preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
Figures la to Id show the schematic plan views of the raceway based steering actuation and linkage mechanisms according to the first aspect of the disclosure, at different articulated positions of the drive vehicle with reference to the centerline of the semi-trailer unit. The actuation mechanism has a drive shaft housing 1 rigidly attached to a turn table 14. The articulation of the prime mover rotates the drive shaft housing 1 and the turn-table 14 together through a steering wedge W. The drive shaft 2 is in operative association with the drive shaft housing 1 and can slide inside the drive shaft housing 1 without rotating about its own axis during operation. Steering wedge W is integrated on the turn table, in operative association with the fifth wheel coupler (Figure 8) mounted on the prime mover. The butterfly housing 3 is pivoted on the gooseneck structure GS and incorporates the main body 18 and cylinder mounting brackets 19. The butterfly housing 3 is in operative association with the driven shaft 4 as well as with the hydraulic actuation cylinders 9. The driven shaft 4 can slide inside the butterfly housing 3 and is in operative association with the drive shaft 2 through a centre pin 5, which is in turn in operative association with a raceway 6 through a centre roller 7. The raceway 6 is bolted on the gooseneck structure GS. The profile of the raceway 6 is designed to control the cutoff limits of steering actuation and also to generate a linear relationship between the prime mover articulation angle and the strokes of the hydraulic actuation cylinders 9.
In Figure la the actuation mechanism is in a straight ahead position, so that the longitudinal axis of the prime mover is in line with the longitudinal axis of the semitrailer unit. In this position the drive shaft 2 and the driven shaft 4 are in straight

ahead position and the centre pin 5 with a centre roller 7 is centrally located in the raceway 6.
Figure lb shows the prime mover steered to the left to an angle corresponding to the cut-off limit, the turn-table 14 rotates in a counter clockwise direction about the fifth wheel centre. The drive shaft housing 1 rotates with the turn-table 14 and causes the drive shaft 2 and pin 5 to rotate on the fifth wheel centre. Since, the centre pin 5 is in operative association with raceway 6 through the centre roller 7, the raceway 6 does not allow it to rotate in a circular locus on the the fifth wheel centre, rather it constrains the centre pin 5 and the centre roller 7 to translate along the profile of the raceway 6. This movement of the center pin 5 pulls the drive shaft 2 outward from the drive shaft housing 1 and rotates the butterfly housing 3 on its pivot through the driven shaft 4.
This rotation of the butterfly housing 3 generates differential strokes in the actuation cylinders 9 and hence the rotation of turn-table 14 and thereby, an articulation of the prime mover is sensed. The driven shaft 4 is also pulled outward from the butterfly housing 3 due to the movement of the centre pin 5.
The actuation cylinders 9 are in fluid communication with follower cylinders 11 (shown in Figure 2a) by means of a hydraulic inflow and outflow piping, respectively. The differential strokes generated in the actuation cylinders 9 will also generate the same strokes in the follower cylinders 11 and hence articulation of the prime mover causes steering of the semi-trailer wheel stations through follower cylinders 11, which are in an operative association with the steering linkage mechanism of the semi-trailer.
Figures lc and Id show the situation when the vehicle is further steered to the left beyond its cut-off limit. The centre pin 5 with the centre roller 7 continues to follow the profile of raceway 6. At this position, the centre line of the profile and the axis of the butterfly housing 3 become in-line and hence the rotation of the butterfly housing 3 is stopped and only the driven shaft 4 is pulled outwards from the butterfly housing

3. Now the rotation of butterfly housing 3 ceases to generate any further differential stroke in the actuation cylinders 9. In this manner, it permits the articulation of the prime mover without actuating the steering linkage mechanism, i.e. without steering the semi-trailer wheel stations.
Referring now to Figures 2a and 2b and Figure 3 of the accompanying drawings, in which the steering linkage mechanism integrated on the semi-trailer unit having steerable wheel stations, is illustrated. The follower cylinders 11 actuate the pivoted steering butterfly which is in an operative association with the rear and front wheel steering linkage of the semi-trailer unit through tie rods 13. The suspensions are pivoted on the semi-trailer chassis and the steering brackets are attached on each suspension units which are interconnected by tie rods 13. Various positions of the semi-trailer steering are shown. The linkage mechanism also accommodates the opposite rotation of one wheel station during turning. This situation arises since the number of the axle rows are large and the instantaneous centre of rotation of the semi-trailer lies between the axle rows (see Figure 10). It will be appreciated that the constrained movement of the centre pin 5 and the centre roller 7 in raceway 6 provides the straight line characteristic (Figure 9) between the prime mover turning angle and the differential strokes generated in actuation cylinders 9 up to a cut-off limit. This allows designing of the steering linkage mechanism to provide actual turning angles of the semi-trailer wheels in closest proximity with the theoretical turning angles by the follower cylinders 11. The cut-off limit is solely governed by the profile of the raceway 6 and can be altered as per requirement, which provides greater flexibility in design.
Figure 3 shows the above actuation and linkage mechanisms integrated on the tractor semi-trailer unit, in which the drive vehicle is articulated by 40° with reference to the centerline of the semi-trailer unit.
Figures 4a - 4b show the cross-sectional views of the drive shaft housing 1 and the butterfly housing 3.

Figure 5 illustrates the cross-sectional view of the raceway based steering actuation and the linkage mechanisms along a section line A-A shown in Figure la. The drive shaft housing 1 is provided with bushes at front and rear ends. The drive shaft 2 is also supported by bushes. An oil hole is provided at the middle. The butterfly housing 3 is provided with bosses at the front and rear ends to increase the bearing area for the driven shaft 4, which is supported by bushes provided in the front and rear bosses. The driven shaft 4 is connected to the centre pin 5 by a bearing and the centre pin 5 is locked with the drive shaft 2 for rotation. The centre roller 7 is connected with the centre pin 5 through the bush. The butterfly housing 3 is pivoted on the base plate and the top plate is bolted with the semi-trailer structure.
Figure 6 provides the assembly details of the raceway based steering actuation mechanism and linkage mechanism. The butterfly housing 3 is pivoted to the base plate of the gooseneck structure. The rod ends of hydraulic actuation cylinders 9 are connected to the butterfly housing 3 through bearings and the cylinder ends are connected to the semi-trailer structure. The driven shaft 4 is connected to the butterfly housing 3. The assembly of the centre pin 5 and the centre roller 7 with the driven shaft 4 is also illustrated. The raceway 6 is bolted to the base plate.
Figure 7 illustrates the bottom perspective view of the side roller assembly 8 provided on the drive shaft 2 to arrest its rotation about its own axis. The side rollers 8 are assembled on the drive shaft 2 through a pin and roll on the extended platform of the drive shaft housing 1 during rotation of the turn-table 14. In case, the drive shaft 2 tries to rotate on its own axis, one of the side rollers 8 touches the extended platform and stops the rotation.
Figure 8 illustrates the exploded view of the turn-table assembly. The assembly includes the steering actuation mechanism SAM and the steering linkage mechanism SLM. The steering actuation mechanism SAM is located on the gooseneck structure GS. The assembly also indicates a turn-table bearing 20 and a king pin 21 located below the turn-table 14.

Figure 9 illustrates the characteristics of the steering actuation mechanism. The stroke generated in the actuation cylinders varies almost linearly with the increase in the turn table rotation angle. The same linear characteristics will be transferred to the steering linkages through the follower cylinders i.e. the actual rotation angle of the wheel stations will vary linearly with the increase in stroke of the follower cylinders. With these characteristics, close proximity between the actual and theoretical steering angles can be obtained by a proper design of the link lengths and tie rods.
Figure 10 shows the steering diagram of the vehicle. The steering at the gooseneck structure is shown by 23 and steering at the trailer is shown by 24. These two positions are on either side of a fixed axle line 22. The steering linkage mechanism according to the present disclosure, by careful design, optimizes the steering angles on all the wheel stations of the semi-trailer to achieve close proximity with the theoretical steering angles.
The present disclosure is a profiled raceway based steering actuation mechanism the raceway profile of which controls the limits of the steering actuation and also generates a linear relationship between the prime mover articulation angle and the differential strokes generated in the hydraulic cylinders.
The cut off limit of the steering actuation is achieved by designing the profile of the raceway and it is so designed that an optimum maneuverability of the prime mover and the semi-trailer is obtained while negotiating the tuning and further steering actuation does not improve maneuverability.
The linear relationship controls the difference between the actual angle of incidence and the theoretical angle of incidence of steerable semi-trailer wheels and also helps in reducing the off tracking of the train.
The disclosure also relates to the steering linkage mechanism provided in the semitrailer for rotation of the steerable semi-trailer wheel stations. The mechanism uses a single steering butterfly for actuation of linkage. The linkages are so arranged as to cater to the reversing of direction of rotation of the wheel stations on either side of

the instantaneous centre of rotation of the semi-trailer. The linkage mechanism is designed to produce the actual angles of wheel stations in closest proximity with the required theoretical angles. Steering linkage for seven wheel stations is shown. However, a similar concept may be adopted for a semi-trailer with more number of wheel stations. Similarly, the present mechanism is not bound by the number of axles and may be used for semi-trailers having more number of axles also.
The term steerable wheel stations comprises of a knee type suspension pivoted to the semi-trailer chassis, stub axle and four wheels. The pivoted suspension provides an independent directional displacement of each suspension unit.
TECHNICAL ADVANTAGES & ECONOMIC SIGNIFICANCE
The technical advantages of the raceway based steering actuation mechanism for steering of trailer include the following:
It controls the limits of steering actuation and also generates a linear relationship between prime mover articulation angle and differential strokes generated in hydraulic cylinders.
It obtains optimum maneuverability of the prime mover and semi-trailer, wheil negotiating turning.
It provides rotation of steerable semi-trailer wheel stations by using single steering butterfly for actuation of linkages.
It is suitable for steering high, very large and extra-long payloads to be carried by
road.
It is suitable for obtaining the desired stroke-articulation angle characteristics.
It avoids the situation wherein a compromise to be made with the structural strength of semi-trailer.
Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or

steps.
The use of the expression "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results. Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.
While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.
We claim:
1. A steering actuation and linkage mechanism for steering of a multi-axle semi-trailer which is coupled to the fifth wheel coupler of the prime mover and the steerable wheel stations of the multi-axle semi-trailer unit, said steering

actuation mechanism comprises:
a. a drive shaft housing (1) having an extended platform, coupled to a
drive shaft (2) provided with side rollers (8), said drive shaft housing
rigidly attached to a turn-table (14) fitted with a steering wedge (W) and
rotating on said fifth wheel coupler;
b. said drive shaft (2) coupled to be slidable inside said drive shaft
housing (1) without rotating on its own axis during the operation;
c. side rollers assembly (8) on said drive shaft (2) assembled through a
centre pin (5), said centre pin engaged with profiled raceway (6) through
a centre roller (7), said raceway (6) bolted to the base plate of a semi
trailer gooseneck structure (GS);
d. a butterfly housing (3) pivoted on said gooseneck structure (GS) and
incorporating a main body (18) and cylinder mounting brackets (19),
said butterfly housing (3) coupled to said centre pin (5) through said
driven shaft (4) and a plurality of hydraulic actuation cylinders (9); said
driven shaft (4) slidable inside said butterfly housing (3),
wherein the profile of said raceway (6) is configured to control the cut-off limits of said steering actuation mechanism, in order to generate a linear relationship between the articulation angle of the prime mover and the different strokes of said hydraulic actuation cylinders (9).
2. A steering actuation and linkage mechanism as claimed in claim 1, wherein the limited rotation of said pivoted butterfly housing (1) and the different strokes generated in said actuation hydraulic cylinders (9) are controlled by said centre pin (5) and a centre roller assembly moving in said profiled raceway (6).
3. A steering actuation and linkage mechanism as claimed in claim 1, wherein said profiled raceway (6) is configured to define the automatic cut-off limit of said semi-trailer steering and said cut-off limit is altered by changing the profile of said raceway (6).

4. A steering actuation and linkage mechanism as claimed in claim 1, wherein the linear relationship between the articulation angle of the prime mover and said differential strokes in said actuation hydraulic cylinders (9) up to said cutoff limit is defined by the configuration of said profiled raceway (6) and wherein the articulation of said prime mover beyond said cut-off limit is allowed without causing any further steering of said semi-trailer unit.
5. A steering actuation and linkage mechanism as claimed in claim 1, wherein said drive shaft (2) is supported by bushes provided on the front and rear ends of said drive shaft housing (1) and respective oil holes provided in the middle of said bushes.
6. A steering actuation and linkage mechanism as claimed in claim 1, wherein said driven shaft (4) is supported by bushes provided in the bosses disposed at the front and rear ends of said butterfly housing (3).
7. A steering actuation and linkage mechanism as claimed in claim 1, wherein said linkage mechanism is integrated on the semi-trailer unit having steerable wheel stations of said multi-axle semi-trailer unit coupled to the fifth wheel coupler of said prime mover, said linkage mechanism comprises:
a. steering brackets (15) mounted on all the wheel stations on each
suspension unit which are interconnected by means of a plurality of tie
rods (13);
b. a pivoted steering butterfly housing (16) coupled to various steering
brackets (15) through said tie rods (13); and
c. a plurality of follower hydraulic cylinders (11) coupled to a steering
butterfly housing (16) to receive the hydraulic actuation generated by
said steering actuation mechanism as claimed in claims 1 to 4 and to
actuate said steering linkage mechanism.
8. A steering actuation and linkage mechanism as claimed in claim 6, wherein
all the wheel stations of the semi-trailer unit are steered through said single

steering butterfly (16).
9. A steering actuation and linkage mechanism as claimed in claim 6, wherein
the reversing of the direction of rotation of the wheel stations on either side of
the instantaneous centre of rotation of the semi-trailer is enabled by said
steering linkage mechanism,
10. A steering actuation and linkage mechanism as claimed in claim 1, wherein
said turn-table (14) assembly comprises said drive shaft housing (1) disposed on
a base structure and a king pin flange disposed in a central aperture on the front
turn-table and a steering wedge (W) bolted to said turn-table (14) to be engaged
with said fifth wheel coupler of said prime mover.