A RETROFIT ABLE RETRACTABLE SUSPENSION SYSTEM FOR A MULTI AXLE VEHICLE
Field of invention
The present invention relates to a retrofitable retractable suspension system for a multi axle vehicle. The suspension system of the present invention is a simple pneumatically operated mechanical system. It is used for lifting and lowering the auxiliary axle of a multi axle vehicle when necessary.
Background of the Invention
FIG. la and b show the schematic of a multi axle vehicle in normal operating condition (i.e., auxiliary axle ungifted condition) and auxiliary axle lifted condition, respectively. The purpose of suspension in a vehicle is to protect the body from shock experienced due to rough road surface. Moreover, it protects the goods and improves ride quality of vehicle by reducing vibration. The multi axle vehicle has been designed and developed to carry heavy loads such as oil, gas, coal, etc. In order to carry such heavy loads, one or more auxiliary axles [1] are added to the standard front [2] and /or rear drive axles [3] of the vehicle without increasing maximum permissible load on each wheel and tires assembly of the vehicle. This type of arrangement is disclosed in U.S Pat. 4165884, U.S Pat. 6883813 B2. These auxiliary axles usually have their own set of leaf springs [4] and /or air bellows, wheels and tires [5]. In order to engage the tires [5] of the axles to the road surface in the leaf spring suspended vehicle, the axles are interconnected through a tie rod [6], bell crank [7] and shackle [8], thereby the load that acts on rear side of the vehicle is equally distributed to both the rear drive and auxiliary axles (FIG 2 a and b). Therefore, the multi axle vehicles are capable to carry large amount of load. However, high fuel consumption, low tire life and low maneuverability (ride quality) are the important issues associated with the multi axle vehicles. In addition, cornering of the vehicles is also difficult as explained in U.S. Pat. 3285621, U.S Pat. 6883813 B2.
In order to reduce the above said issues associated with multi axle vehicle, the auxiliary axles can be lifted from the road surface during the return trip of the vehicle

if the vehicle is empty or contains less load. The mechanism should be designed in such a way that when the auxiliary axle [1] is lowered into road engagement, the leaf spring suspension should work properly and distribute the load to both the rear and auxiliary axle. When the auxiliary axle is not needed, for example in unlade condition, the designed mechanism can lift the tires of auxiliary axle from the road surface to a sufficient height and maintain them at this position. Thereby, irregular road contact can be prevented on the auxiliary axle; even when the vehicle is operated on the undulated and humped roads. In this way, life of tires and brakes and its associated components can be increased. Moreover, the better fuel economy and maneuverability can also be achieved.
Generally, leaf spring suspension and air spring suspension are two prominently used suspension systems in multi axle vehicles. As the cost of leaf spring suspension is relatively less than the cost of air spring suspension, the leaf spring suspension is most commonly used in heavy duty vehicles. Implementation of a lifting system with the air spring suspension is relatively simple and also commercially viable because force required for lifting the auxiliary axle assembly (i.e., auxiliary axle, wheel and tires) is less. One such system is disclosed in US Pat. 6,883,813. However, retrofitable retractable system is not commercially available. Most of the liftable auxiliary axles utilize one or more air springs to lift or lower the auxiliary axle. A numerous types of auxiliary lift axle suspension systems have been designed (U.S Pat. Nos: 3502348; 3704896; 4165884). These lifting systems suffer from several problems. One of the problems is that the lifting mechanism is subjected to failure and expensive for maintenance. In addition, the lifting mechanism is relatively heavy, which makes difficult to handle. However, only a few types have been recognized to implement. In this respect, a few commercially acceptable designs are: (1) use of inverted leaf spring accompanied by an air bellows (U.S. Pat. 3285621) and (2) parallelogram lift axle suspension system disclosed by Chaplin et al (U.S. Pat. 6957819 B2) and Gottschalk (U.S. Pat. 5403031), and (3) Lift axle air pressure transfer control apparatus (U.S. Pat. 6845989 B2). In the suspensions, an expandable and retractable air bellow system are used, in which one air bellow would be expanded to lower,

while another air bellow would be expanded to lift the auxiliary axle from road surface. These lifting systems also suffer from few problems such as low life of the air bellows and pivot brackets and heavy weight (U.S. Pat. 6883313 B2). In addition, U. S. Pat. 4773670 and 6158750 have proposed a different mechanism, in which two lifting air bellows are used and they are mounted in vertical position. The air bellow and its associated structures and control mechanism increases the cost of the vehicle. In addition, the systems are complicated and that makes them unreliable (U.S. Pat. 2007/0108711 Al). Furthermore, U.S Pat. 2007/0108711 is proposed to use one air bellow to lift the axle. However, it can be used in air spring suspension vehicle only.
On the other hand, different types of hydraulic liftable auxiliary axle are also proposed in U.S Pat.: 4102424; 4165884; 3936072; 4842302; 3925470 and Indian patent application no. 1013/CHE/2006. These lifting systems also suffer from several problems such as large space requirement, heavy construction and are relatively expensive to install [U.S. Pat. 4102424]. 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 road surfaces. Such shock forces may damage all the components of lifting system. This leads to high maintenances and expensive repairs (U.S. Pat. 4134604). Moreover, all the components of lifting mechanism are also subjected to side thrust forces (i.e., lateral forces) while the vehicle is cornering. The side thrust forces produce a high strain on the hydraulic cylinder seals, which leads to premature failure of the hydraulic cylinder (U.S. Pat. 4134604). This side thrust can cause premature wear of pivot bushing and other components of the air spring liftable suspension system (U.S. Pat. 6957819 B2).
Design and implementation of a retrofit retractable suspension system in the leaf spring suspension vehicle is relatively difficult, because a large force is required to lift the auxiliary axle against the force of the leaf springs. Therefore, the lifting and lowering mechanism should be designed and developed in such a way that it should withstand the shock load, side thrust load and lift a required height from the road surface and maintain the axle in the lifted position. Furthermore, it should be installed in the vehicle without modification of existing components of multi axle vehicle.

When a multi axle vehicle operates in unladed condition, the tire life, fuel economy, ride quality will suffer due to addition of the auxiliary axles. However, the liftable auxiliary axle can minimize the effect of adding such auxiliary axle.
Low space available at the chassis frame and auxiliary axle is an important parameter which limits the mounting of a lifting mechanism. In automobile industries, pneumatic system is highly attractive because it reduces the vibration and dynamic load and withstands the shock loads. It can also be fitted by semiskilled workers. Moreover, when a heavily loaded vehicle gets mired in a slush or pot hole, it is desirable to lift the auxiliary axle temporarily to transfer load to the rear drive axle tires and thereby enable the rear drive axle tires to produce sufficient traction.
In this perspective, the present invention proposes a simple, highly reliable, low cost, retrofitable suspension to lift and lower the auxiliary axle of a multi axle vehicle.
Summary of invention
The present invention describes a simple pneumatically operated system for lifting and lowering the auxiliary axle of a multi axle vehicle. The mechanism can be mounted in retrofitable manner to the conventional leaf spring suspension of a multi vehicle. The mechanism has few parts and consumes relatively less space. The operator (i.e., drivers) of the vehicle can lift and lower the auxiliary axle from cabin. Further more, the suspension system of present invention is applicable to all kinds of multi axle vehicles.
The prime object of this invention is to provide a simple mechanism to lift the auxiliary axle to a height of -165 mm from the road surface at low cost, low maintenance with few number of components.
Another object of the present invention is to provide a simple mechanism which can be operated by normally available compressed air in a vehicle with an additional air storage cylinder.

Another object of the present invention is to provide such a mechanism that is manual in- cab control over the auxiliary axle
Another object of the present invention is to provide a mechanism which can be retrofit ably mounted to the chassis frame and auxiliary axle.
Another object of the present invention is to provide a mechanism that is easily mounted in the vehicle with out modify the existing components of the vehicle.
Another object of the present invention is to provide a simple mechanism that is highly reliable.
Another object of the present invention is to provide a simple mechanism that withstands dynamic loads.
Another object of the present invention is to provide a simple mechanism that can be easily manufactured.
Another object of the present invention is to provide a simple mechanism that can be implemented in all kinds of multi axle vehicle, which has auxiliary axles.
Yet another object of the present invention is to provide a simple mechanism that can be accommodated within chassis and consumes less space.
Brief description of the accompanying drawings :
This invention is now described with reference to the figures in the accompanying drawings:
FIGURE 1 shows a multi axle vehicle: (a) auxiliary axle in normal condition and (b) auxiliary axle in lifted condition.
FIGURE 2 shows a non reactive bell crank lever and tie rod auxiliary axle suspension.

FIGURE 3 shows the suspension system of the present invention fitted in the vehicle (viewed from rear side).
FIGURE 4 shows the model of the suspension system in the chassis frame of a multi axle vehicle.
FIGURE 5 shows the model of the assembly of housing, air bellow and pulling plate of the suspension system of the present invention.
FIGURE 6 shows the suspension system, which is just about to lift the auxiliary axle.
FIGURE 7 shows the suspension system, which is in auxiliary axle lifted position.
Detailed description of the present invention:
FIG. 3 shows the schematic of the simple mechanism of the suspension system for lifting and lowering the auxiliary axle of a multi axle vehicle. The present invention is to be incorporated to the auxiliary axle of a multi axle vehicle. It can be mounted in the chassis frame.
FIG. 4 shows the model of the proposed system in the chassis frame of a multi axle vehicle. The suspension system of the present invention comprises upper cross member [9], two lower cross member [10], air bellow [11], housing [12], pulling plate [13], wire rope [14], hook [15], U clamp [16], clamp plate [17], solenoid two ways valve (i.e., flow control valve)[18] and hose [19]. The cross members [9, 10] are used to carry all the components of the mechanism. The upper cross member [9] and lower cross member [10] are made of mild steel. Both ends of the cross members are attached to the chassis frame [20] of the vehicle by conventional fasteners such as bolts and nuts in such a way to form an enclosure between them just above the auxiliary axle. The air bellow [11] and pulling plate [13] are placed inside of the housing [12] as shown in FIG. 5. The pulling plate comprises two extended members (13a, 13b) with a hole (28) in the side walls. The housing [12], pulling plate [13] are

made of steel. The housing [12] is mainly used to hold the air bellow [11] and prevent the failure of air bellow caused by thrust force. The housing has two rectangular slots [21], which is used to guide the extended members (13a, 13b) of the pulling plate [13]. The housing [12] is connected to the upper cross member [9] by means of mechanical fasteners. To give a proper support to the housing [12], two lower cross members [10] are used, which is connected to the chassis frame [20] by fasteners. The air bellows [11], housing [12] and cross members [9, 10] have to withstand large dynamic and static loads after lifting the auxiliary axle from the road surface. Therefore, connecting rods [22] are used to connect the both upper and lower cross members rigidly. The pulling plate [13] is connected to the auxiliary axle [1] by means of wire rope [14] and hook [15]. The wire rope is preferably made of cold drawn alloy steel wires, which gives high strength and durability. While operating the vehicle over humps, pot holes and irregular road (i.e., rough road surface), both the tires [5] of the auxiliary axle [1] will move upward and downward to follow the road contours accordingly. During this movement, force exerted in the axle should not transfer to the chassis frame. The wire ropes [14] are, therefore, used to connect the pulling plate [13] and auxiliary axle [1], as the wire rope is more flexible and has tendency to spin. The hook [15] is made of forged steel. A clamping device is also used to clamp the auxiliary axle rigidly, which consists of a U clamp [16] and clamp plate [17] and bolts and nuts [23].
The solenoid two ways valve [18] and hose [19] are used to supply compressed air from an air storage tank (not shown) of the vehicle to the air bellow as well as remove the air from the air bellow through an opening (27). The solenoid valve [18] is connected to the battery of the vehicle.
The entire assembly is mounted below the load body [24], The top surface of the upper cross member [9] is below the chassis sub frame [25], which is mounted on the chassis frame [20]. To avoid direct contact, sufficient gap is provided between the load body [24] and upper cross member [9].
Working principle of the invention
Vehicle operating in auxiliary uplifted condition:

FIG.6 shows the schematic of the proposed system in auxiliary axle unlifted condition. When the vehicle operates in the laden condition, the tires of the both rear drive and auxiliary axles have to engage to road surface. So that, the load that acts on rear side of the vehicle is equally distributed to these two axles. The compressed air from the air bellow is released to escape to atmosphere through the solenoid valve [15]. Due to decrease the pressure and quantity of the air in the air bellow, the pulling plate is moved downward. Therefore, the tires of the auxiliary axle are engaged to road surface
Operating the vehicle in auxiliary axle lifted condition:
FIG.7 shows the schematic of the proposed system. During lifting the auxiliary axle, certain quantity of compressed air at a pressure of 8 xlO 5 N/m2 (~ 8 bar) is supplied to the air bellow from the compressed air storage tank through the solenoid valve, making the air bellow expand in vertical upward direction. The solenoid valve is operated by driver from the driver cabin of the vehicle. Expansion of the air bellow causes the pulling plate to move upward. Consequently, the auxiliary axle is lifted upward. Therefore, the tires of the auxiliary axle are disengaged from road surface. Therefore, the entire auxiliary axle assembly is lifted above the road surface and maintained at a required distance from the road surface. As the entire auxiliary axle assembly is suspended over the compressed air filled air bellow and hanged by wire rope, the damage of components caused by shock loads and side thrust loads can be prevented.
The foregoing description is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purpose of illustration only, and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.

WE CLAIM :
1. A retrofitable retractable suspension system for lifting or lowering an auxiliary
axle (1) of a multi axle vehicle, said system comprising
an upper cross member (9) and at least one lower cross member (10) fixed between the chasis frame (20) of the vehicle in such a manner to form an enclosure (26) between said upper cross member (9) and said lower cross member (10) above said auxiliary axle (1);
a housing (12) positioned in said enclosure (26) with the top end of the housing (12) being fastened to the upper cross member (9) and the lower end of the housing being fastened to the lower cross member (10), the housing having two vertical slots (21) positioned diagonally opposite to each other;
an air bellow (11) placed inside the housing (12), the air bellow (11) having at least one opening (27) for compressed air to pass through;
a pulling plate (13) positioned on top of the air bellow (11) inside the housing (12) in such a way that the pulling plate is moved upwards or downwards by applying or withdrawing the compressed air to the air bellow (11), the pulling plate having two extended members (13a, 13b) arranged to slide in the slots (21) of the housing (12);
a pair of wire rope (14) , one end of each of the wire rope being connected to the extended members (13a, 13b) of the pulling plate (13) and the other end of each of the wire rope being connected to the auxiliary axle (1) for lifting or lowering the auxiliary axle (1) when the pulling plate (13) is moved upwards or downwards.
2. The system as claimed in claim 1, wherein the wire rope (14) is connected to the auxiliary axle (1) using a hook (15), U clamp (16) and clamp plate (17).
3. The system as claimed in claim 1, wherein a solenoid valve (18) is connected at the opening (27) of the air bellow (11).

The system as claimed in claim 1, wherein the solenoid valve (18) is connected to an air storage tank through a hose (19).
The system as claimed in claim 1, wherein the upper cross member (9) and lower cross member (10) are held together by a connecting rod (22) for additional support.
The system as claimed in claim 1, comprising two lower cross members (10).
The system as claimed in claim 1, wherein the housing (12) and the pulling plate (13) are in circular shape.
The system as claimed in claim 1, wherein the extended member of the pulling plate (13) comprises a hole (28) for the wire rope (14) to pass through.
The system as claimed in claim 1, wherein the wire rope (14) is made of cold drawn alloy steel wires.
The system as claimed in claim 1, wherein the upper cross member 99) and the lower cross member (10) are made of mild steel, the housing (12) and the pulling plate (13) are made of steel.