FIELD OF THE INVENTION
The present invention relates to a retrofit retractable suspension mechanism for lifting and lowering the auxiliary axle of a multi axle vehicle.
PRIOR ART
The purpose of suspensions is to protect the automobile body from shock forces. Moreover, it protects the goods and improves the quality of ride by reducing vibration. Figure la and lb show the conventional schematic of a multi axle vehicle in auxiliary axle normal and lifted conditions, respectively. The multi axle vehicle is used for transportation of cement, steel, coal, oil (petroleum product), iron ore, etc. In order to carry such large loads, one or more auxiliary axles 1 are added to standard front 2 and/or rear drive axles 3 of the vehicle without increasing the maximum permissible load on each wheel/ tires as disclosed in US4165884 and US6883813B2. According to figure 2, the auxiliary axle normally has their own set of leaf springs 4, wheels and tires 5. In order to engage the tires 5 of these axles to road surface, they are interconnected through a tie rod 6, bell crank 7 and shackle 8, thereby the load which acts on rear side of the vehicle is equally distributed to these axles. Therefore, the multi axle vehicle is capable to carry a large amount of load. However, high fuel consumption, poor tire life and low maneuverability (ride quality) are important issues associated with the multi axle vehicles. Moreover, cornering of the vehicle is difficult which is disclosed in US3285621, US6883813B2, and US6769703Bl.
In order to reduce the above-described problems associated with the multi axle vehicles, the auxiliary axles can be lifted off the road surface during a partially (lighdy) loaded condition and/or unlade condition (i.e., period of empty) of the vehicle, using a suitable mechanism.
Generally, leaf spring and air spring suspensions are most commonly used in the multi axle vehicles. Implementation of a retractable system (i.e., lifting system) in the air spring suspension vehicle is relatively simple and also practically possible which is disclosed in US6883813B2. Numerous types of lift axle suspension systems have been designed which are disclosed in US3502348, US3704896 and US4125884. One of the problems associated to such lifting mechanisms is that the mechanism is subjected to failure and expensive to replace. In addition, the lifting mechanism is relatively heavy, which makes difficult to handle. However,
2

only a few types have been recognized for implementation. The commercially acceptable designs are: (1) use of inverted leaf spring accompanied by an air bellows (US3285621) and (2) parallelogram lift axle suspension system disclosed by Chalin et al. (US6957819B2) and Gottschalk (US5403031), which is commercially known as the Hendrickson ParaliftTM and Paralift UltraTM steerable and non steerable lift axle suspension systems and (3) Lift axle air pressure transfer control apparatus (US6845989B2). In the suspensions, an expandable and retractable air bellows are used, in which one air bellow is expanded to lower, while another air bellow is to lift the auxiliary axle from road surface. These lifting systems also suffer from problems such as low life of the air bellow and pivot brackets as disclosed in US6883313B2.
A number of different types of hydraulically liftable auxiliary axles are disclosed in US4102424, US4165884, US3936072, US4842302 and US3915470 and Indian Patent Application No. 1013/CHE/2006. The lifting systems also suffer from several problems such as heavy construction and relatively expensive as disclosed in US4102424.
A problem associated with the liftable auxiliary axle is that the lifting mechanism is subjected to extremely high shock forces when the vehicle is operated over undulated roads. The shock forces are transmitted to all the components of lifting mechanism as well as the axle assemblies too. Such shock forces may damage the components of lifting mechanism, including hydraulic cylinders. It leads to high maintenances as disclosed in US4134604. Moreover, the all components lifting mechanism are also subjected to side thrust forces (i.e., lateral forces) while the vehicle cornering. The side thrust forces produce a high strain on the cylinder seals, which leads to a premature failure of the hydraulic cylinder is disclosed in US4134604. This side thrust can also cause premature wear of pivot bushing and other components of the air spring liftable suspension system is disclosed in US6957819B2.
Implementation of a retrofit retractable suspension system in a conventional leaf spring suspension vehicle is relatively difficult, because a large force is required to lift the auxiliary axle against stiffness of the leaf springs. In addition, the auxiliary axle is interconnected with rear drive axle 3.

SUMMARY OF THE INVENTION
It is therefore, the prime object of the invention is to provide a retrofit retractable suspension mechanism for lifting and lowering the auxiliary axle to a required distance from the road surface of a multi axle vehicle having a simple pneumatically operated mechanism.
Another object of the invention is to provide a retrofit retractable suspension mechanism for lifting and lowering the auxiliary axle of a multi axle vehicle having low manufacturing cost since the mechanism works with less number of components.
Yet, another object of the invention is to provide a retrofit retractable suspension mechanism for Ufting and lowering the auxiliary axle of a multi axle vehicle having a mechanism, which is retrofit ably mountable to the chassis frame of the multi axle vehicle.
A further object of the invention is to provide a retrofit retractable suspension mechanism for Ufting and lowering the auxiliary axle of a multi axle vehicle, which is operated by compressed air, having high durability and high reliability and requires less space.
A further object of the invention is to provide a retrofit retractable suspension mechanism for Ufting and lowering the auxiliary axle of a multi axle vehicle wherein the driver of the vehicle actuates the mechanism from driver cabin itself that avoids spending manual effort for lifting the auxiliary axle.
A further object of the invention is to provide a retrofit retractable suspension mechanism for Ufting and lowering the luxury axle of all kinds of multi axle vehicle, which has an luxury axle.
A further object of the invention is to provide a retrofit retractable suspension mechanism for Ufting and lowering the luxury axle of a multi axle vehicle that can be easily mounted in the vehicle with out modification of components.

A further object of the invention is to provide a retrofit retractable suspension mechanism for lifting and lowering the auxiliary axle of a multi axle vehicle which is having a simple mechanism that withstands dynamic loads.
Accordingly, the present invention provides a retrofit retractable suspension mechanism for lifting and lowering the auxiliary axle of a multi axle vehicle, comprising: an upper cross member and a lower cross member having both the ends connected to the chassis frame of the vehicle by fasteners; ad east two identical air cylinders having a reciprocating piston are connected to the upper cross member by fasteners; the reciprocating piston is connected to the auxiliary axle through the connecting rod and a wire rope; the auxiliary axle having a U clamp and a clamp plate; a solenoid valve for supplying compressed air from the air cylinder; and bolts for holding the upper cross member.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The advantages and features of the invention will become more clearly apparent from the following description, which refers to the accompanying drawings given as non-restrictive examples only and in which:
Figure 1 shows the conventional schematic of a multi axle vehicle: (a) auxiliary axle in
normal condition and (b) auxiliary axle in lifted condition.
Figure 2 reflects the conventional schematic of a non reactive bell crank lever and tie rod
auxiliary axle suspension.
Figure 3 illustrates the schematic of the novel mechanism in the vehicle (viewed from rear
side) according to the present invention.
Figure 4 shows the model of the present system in the chassis frame of a multi axle
vehicle.
Figure 5 shows the schematic of the proposed system in auxiliary axle lifted condition.
Figure 6 shows the schematic of the proposed system in auxiliary axle unlifted condition
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Figure 3 shows the schematic view of a retrofit retractable suspension mechanism for lifting and lowering the auxiliary axle of a multi axle vehicle which is mounted to the chassis frame of the vehicle.
Figures 4 to 6 shows the constructional details of the mechanism of the present invention. The present mechanism consists of upper cross member 9, lower cross member 10, adeast two air cylinder 11, wire rope 12, U clamp 13, clamp plate 14 and two ways solenoid valve (i.e., flow control valve) 15. The upper cross member and lower cross member are made of steel. The cross members carry all the components of the mechanism. Both ends of the cross members are connected to the chassis frame 16 of the vehicle by means of conventional fasteners. The two identical air cylinders 11 are connected to the upper cross member 9 by means of fasteners. The air cylinder 11 consists of a reciprocating piston 18, housing 19, connecting rod 20, tube 21 and rubber pad 22. The housing 19 is made of steel and has an air vent 24 on its top side. It is used to vent air to atmosphere while the reciprocating piston moves upward. The reciprocating piston 18 is connected to the auxiliary axle 1 through the connecting rod 20 and a wire rope 12. The wire rope is made of cold drawn alloy steel wires, which gives a high strength and durability. The wire ropes are provided for more flexibility. The mechanism is designed in such a way that the connecting rod, reciprocating piston and the air cylinder do not encounter dynamic loads when the vehicle travels on uneven roads. A rubber pad 22 is also provided inside of the air cylinder to avoid direct contact of housing 19 and reciprocating piston 18, so that tear (i.e., damage) of tube can be prevented. In addition, a rubber coating 23 is used on the connecting rod and inside of the air cylinder. Purpose of the rubber coating is to prevent failure of the tube. A clamping device is also used to clamp the auxiliary axle rigidly. It consists of a U clamp 13, clamp plate 14 and bolts and nuts. The bolts are used to hold the auxiliary axle 1 and clamp plate 14. The solenoid valve 15 is used to supply compressed air from air storage tank of the vehicle to the tube 21. The solenoid valve is powered by the battery of vehicle, which can be operated from the driver cabin itself.
Working principle of the mechanism:

Operating the vehicle in auxiliary axle lifted condition:
Figure 5 shows the schematic of the proposed mechanism in unlade condition. During lifting the auxiliary axle, compressed air, at a pressure of ~ 8 x 10 5 N/m2 (~ 8 bar), is supplied to the tube 21. As air inflates the tube, it pushes the reciprocating piston upward. Consequently, the axle is lifted against the spring force. Therefore, the tires of the auxiliary axle are disengaged with road surface. As the entire auxiliary axle assembly is suspended over the compressed air filled tube 21 and hanged by the wire rope 12, damage of components caused by shock loads and side thrust loads can be prevented.
Operating the vehicle in auxiliary axle unlifted condition:
Fgure.6 shows the schematic of the proposed mechanism during operating the vehicle in laden condition. The air, from the tube, is released to atmosphere through the solenoid valve 15. Due to decrease the pressure and quantity of the air, the reciprocating piston 18 and connecting rod 20 assembly is moved downward by the action of leaf springs. Therefore, the tires of the auxiliary axles are engaged to the road surface. However, a required pressure air is maintained in the tube to suspend the reciprocating piston 18 and connecting rod 20. It is mainly used to prevent the damage of the tube caused by impact of piston when the vehicle moves over rough terrain (i.e., uneven road surface). In addition, the translated motion (i.e., upward and downward) that occurred in the auxiliary axle 1 will not be transferred to the piston and connecting rod, because during moving the vehicle on the such undulated road, both the drive and auxiliary axles similarly follow the road surface contour.
Application requirements:
When a multi axle vehicle operates in unlade condition, the tire life, fuel economy, ride quality and traction in rear drive axle are decreased due to the auxiliary axles. The choice of having a liftable auxiliary axle can minimize the effect of the auxiliary axles in the multi axle vehicle. As both the rear drive and auxiliary axles are interconnected through a tie rod and bell crank lever and shackle, a large force is required to lift the auxiliary axle.
From the automobile industry perspective, pneumatic mechanism is highly attractive because it reduces the vibration and withstands the shock loads. Moreover, a semiskilled operator can also operate it. In this view, the present invention is proposed a simple, retrofitable, dash board operate able (i.e., cab control) mechanism for lifting and lowering the auxiliary.


Though the present invention was shown and described with reference to the preferred embodiment, such are merely illustrative of the present invention and are not to be construed as limitation thereof and various modifications of the present invention will be apparent to these skilled in the art. It is, therefore not intended that the present invention be limited to the disclosed embodiment or details thereof, and the present invention includes all variations and/or alternative embodiments within the spirit and scope of the present invention as defined by the appended claims.

WE CLAIM:
1. A retrofit retractable suspension mechanism for lifting and lowering the auxiliary axle of
a multi axle vehicle, comprising:
an upper cross member (9) and a lower cross member (10) having both the ends connected to the chassis frame (16) of the vehicle by fasteners;
atleast two identical air cylinders (11) having a reciprocating piston (18) are connected to the upper cross member (9) by fasteners;
the reciprocating piston (18) is connected to the auxiliary axle (1) through the connecting rod (20) and a wire rope (12);
the auxiliary axle (1) having a U clamp (13) and a clamp plate (14);
a solenoid valve (15) for supplying compressed air from the air cylinder (11); and
bolts (17) for holding the upper cross member (9).
2. The retrofit retractable suspension mechanism as claimed in claim 1, wherein the upper cross member (9) and the lower cross member (10) are made of steel.
3. The retrofit retractable suspension mechanism as claimed in claim 1 or 2, wherein the air cylinders (11) having a housing (19), connecting rod (20), tube (21) and rubber pad (22).
4. The retrofit retractable suspension mechanism as claimed in any one of claims 1 to 3, wherein the housing (19) having an air vent (24) on its top side and made of steel.
5. The retrofit retractable suspension mechanism as claimed in claims 1 and 3, wherein a rubber coating (23) is provided on the connecting rod (20) and inside of the air cylinder (11), which prevents failure of the tube.
6. The retrofit retractable suspension mechanism as claimed in claim 1, wherein wire rope (12) is made of cold drawn alloy steel wires for giving a high strength and durability.

7. The retrofit retractable suspension mechanism as claimed in any one of claims 1 to 6,
wherein the connecting rod (20), the reciprocating piston (18) and the air cylinders (11) do not
encounter dynamic loads while the vehicle is traveling on uneven roads.
8. The retrofit retractable suspension mechanism as claimed in any one of claims 1 to 7,
wherein a rubber pad (22) is provided inside of the air cylinder (11) to avoid direct contact of the
housing (19) and the reciprocating piston (18) for preventing damage of the tube (21).
9. The retrofit retractable suspension mechanism as claimed in any one of claims 1 to 8,
wherein solenoid valve (15) is powered by the battery of the vehicle which is operated from the
driver cabin of the vehicle.
10. The retrofit retractable suspension mechanism as claimed in any one of claims 1 to 9,
wherein the upper cross member (9) and the lower cross member (10) carry all the components
of the mechanism.