Field of invention
[001] The present invention relates to a suspension system and more particularly to a heavy duty lift axle suspension (having dual tires at the each side) used as a pusher axle to a heavy duty multi-axles vehicle (MAV).
Background of invention
[002] Auxiliary axle is generally used in heavy duty trucks to increase load carrying capacity and distribute the load onto the road surface. Generally, trucks having auxiliary axle do not operate in full load condition all the time. It has been found that nearly 20-25% of the time a truck runs empty (i.e., unladen condition). In the empty run condition or partially loaded condition, the service of an auxiliary axle is not required; because, the load acting on each axle is much less than the maximum permissible load of the axles. Thus, one of the axles may be lifted in unladen condition. Such auxiliary axle suspension is known as lift axle suspension.
[003] The lift axle suspension system is usually an air suspension. It is becoming increasingly important in the multi- axle vehicle; because, it extends the tire life and increases fuel efficiency by reducing rolling resistance of the vehicle. The lift axle suspension is usually maintained in the lifted position; until, it service is required.
[004] Trailing arm lift axle (having dual tires at the each side) is commercially accepted for rigid truck application. Usually, this axle is

non-steered type lift axle and it can be located in front of the drive axle (pusher position) or rear side of the drive axle (tag position). Due to packaging difficulty and cost of the trailing arm type steer-axle, self-steerable/power steerable lift axle having drum brake is not used in heavy duty trucks. The position of drum brake in the axle assembly limits the packaging of a steer lift axle assembly in front of the drive axle (i.e., pusher position in the vehicle).
[005] The trailing arm non-steer lift axle is used in trucks for the past decade. The trailing arm lift axle suspension system is exactly that-a suspension arm is joined at the front to the chassis, allowing the rear to swing up and down. More clearly, the trailing arm non-steer lift axle suspension comprises a trailing arm having one end is pivotally connected to the chassis frame through a hanger bracket and another end is connected to the chassis frame by an air spring. A pair of trailing arms supports an auxiliary axle, which includes wheels. Road induced reaction forces acting on the wheels are controlled (withstood) by the pivoting of the trailing arm in response to these forces being resisted by the air spring. If the auxiliary axle is fitted in front of the drive axle, the auxiliary axle is called as pusher lift axle. If the auxiliary axle is fitted behind the drive axle, the auxiliary axle is called as tag lift axle.
[006] Figure 1 illustrates the trailing arm type heavy duty lift axle (1) (prior art) having dual tires (11) used in developed countries such as USA, UK and Australia. It is used as a pusher lift axle for the MAV. The trailing arm lift axle (1) consists of a pair of hanger brackets (2), a

pair of trailing arms (3), a pair of lift air springs (4), a pair of ride air springs (5), a pair of air spring mounting brackets (6), a pair of U bolts (7), circular cross section center drop axle (8), a pair of shock absorber (9) , a pair of dual tires (11) and pivot bolts (12). The hanger brackets
(2) are attached with the chassis side frames (10). The trailing arms
(3) are pivotally connected with the hanger brackets (2) using pivot bolts (12). The ride air springs (5) are mounted at the trailing arm (3) ends and attached with the vehicle chassis frame through the air spring mounting brackets (6). The circular cross section center drop axle (8) is clamped with the trailing arm (3) by using U bolts (7). The lift air springs (4) are mounted at the opposite ends of the ride air spring (5). It is fitted either within the hanger bracket (2) (Figure la) or at the bottom of the trailing arm (3) (Figurelb and c). The shock absorbers are pivotally fitted in between the chassis frame (10) and the trailing arm (3). A lift axle control system and level sensing valve (not shown) are used to maintain a constant ride height of the lift axle in the vehicle. When the vehicle is operated unladen condition, the lift axle control system deflates the ride air spring and inflates the lift air spring. Thereby, the axle is lifted from the road surface.
[007] Few OEMs tried the trailing arm type heavy duty lift axle (1) having dual tires (11) at the each side in developing countries such as in India. However, the trailing arm type lift axle (1) having dual tires is not yet commercially accepted because of its low ground clearance and reversible sleeve air spring, etc. Many failures are observed in the conventional trailing arm rear air suspension system (1) used in the trailer. Especially, failures are observed in the piston and rubber

bellows of reversible sleeve type air spring (that is commonly used in the trailing arm type air suspension). As the trailer experiences mud roads, small debris such as sands, small size stones, small metal pieces, etc., enter into small gap which exists in between the piston and rubber bellows of reversible sleeve air spring. During continuous up and down movement of the piston, the piston as well as rubber bellows are subjected to premature failures due to rubbing action of the small debris (that are stick on the rubber bellows as well as the piston). In addition, the trailing arm lift axle has low ground clearance. Therefore, the conventional trailing arm type lift axle (1) is not suitable for developing countries where the roads are not sufficient enough for the vehicle having low ground clearance.
[008] Although various types of lift axle suspensions have been developed over the past decade in developing countries such as India, parallelogram type steerable suspension system (having single tire on each side) has proved which is the most commercially acceptable for heavy duty vehicle, since it uses convolute type ride air springs. The parallelogram type self-steerable suspension system is commercially being used as pusher lift axle with a maximum load carrying capacity of -6-7T. The parallelogram linkages maintain a uniform distance in-between the top and bottom clamped surfaces of air springs. Thereby, air spring crimping failure and bead plate crack failures are avoided. Therefore, the parallelogram type self-steerable suspension system is the most used and desired system for pusher axle application. [009] Now a day, original equipments manufacturers (OEMs) develop heavy vehicles (having multi-axles) to satisfy customers demand. The

salary of driver is continuously being increased (as availability of driver is reduced). The OEMs are more focusing on developing long heavy duty rigid trucks having maximum allowable load limit. At the same time, they focus on developing low cost and low maintenance vehicles.
[010] Figure 2 is a prior art of a heavy duty multi-axle vehicle (MAV) having configuration of 10x4 with a pusher lift axle. Similarly, heavy duty multi-axle vehicle having configuration of 10x4 with a tag lift axle is being developed. Such vehicles are manufactured in developed countries such as USA and Australia. The vehicle has twin front axles, a trailing arm type lift axle (1) and two tandem rear axles. The trailing arm type lift axle (1) can be lifted in unladen and partially laden condition. The trailing arm type lift axle (1) (prior art Figure la and lb) have circular cross section center drop axle (8) and dual tires (11) at the each side.
[Oil] From the study on the vehicle requirements in developing countries such as INDIA, Pakistan etc., it is observed that a need of higher load carrying capacity MAV. Accordingly, the present invention provides a heavy duty lift axle suspension having dual tires at the each side. More specially, the present invention provides a non-steer pusher lift axle (having dual tires at the each end) for developing heavy duty multi-axle vehicle which meets the legal requirements of developing countries and provides the desirable advantages and objects referred to. In addition, the pusher lift axle has enhanced durability and at the same time cost effective.

[012] Accordingly, the present invention provides a heavy duty lift axle suspension consists of first and second hanger brackets, first and second top control arm assemblies, first and second bottom control arm assemblies, first and second ride air springs, first and second lift air springs, first and second rebound chain assemblies, first and second jounce stopper assemblies, first and second top air spring brackets, eight PU bushing assemblies, a centre drop axle assembly having first and second air spring brackets, an alignment bracket assembly and a pneumatic control system.
[013] The first and second hanger brackets are securely attached with chassis's side members by conventional bolts and nuts. The first top control arms and first bottom control arm are pivotally attached to the first hanger bracket and the first air spring bracket of the centre drop axle assembly using the PU bushing assemblies and pivot bolts. The second top control arms and second bottom control arm are pivotally attached to the second hanger bracket and the second air spring bracket of the centre drop axle assembly using the PU bushing assemblies and pivot bolts. The first ride air spring is securely attached in between the first air spring bracket of centre drop axle assembly and first top air spring bracket attached to the side member of chassis frame. The second ride air spring is securely attached in between the second air spring bracket of centre drop axle assembly and second top air spring bracket attached to the side member of

chassis frame. The first lift air spring is secured in between the first top control arm and first bottom control arm. The second lift air spring is secured in between the second top control arm and second bottom control arm. The first rebound stopper chain assembly is pivotally attached to the side frame of member and first air spring bracket of centre drop axle assembly. The second rebound stopper chain assembly is pivotally attached to the side frame of member and second air spring bracket of centre drop axle assembly. The first jounce stopper assembly is made of a nylon wear pad, a pair of washers and a pair of dowel pins or split pins, is securely attached to the first air spring seating bracket of centre drop axle assembly. The second jounce stopper assembly is similar to first jounce stopper assembly.
[014] The first and second jounce stoppers assemblies and the first and second rebound stopper chain assemblies are used to limit the dynamic travel height of the lift axle suspension when it is operated in undulated roads. The first and second jounce stopper assemblies maintain a desired gap between propeller shaft (not shown) of the vehicle and the centre drop axle is maintained while the axle lifting. The first and second rebound stopper chain assemblies limit the over travel of axle towards downward to prevent the over extension of first and second ride air springs. When lift the axle, the first and second ride air springs are deflated and the first and second lift air springs are inflated using the pneumatic control system.

[015] For better understanding, an illustrative embodiment of the invention is described with reference to the accompanying drawings. It will however be appreciated that the embodiments exemplified in the drawings is merely illustrative and not limitative to the scope of the invention, because it is quite possible, indeed often desirable, to introduce a number of variations in the particular embodiment that has been shown in the drawings.
[016] Figure 1 illustrates the trailing arm lift axle having dual tires at the each side.
[017] Figure 2 illustrates the prior art of a heavy duty multi-axle vehicle (MAV) having configuration of 10x4 with a pusher lift axle operated in developing countries such as USA and Australia.
[018] Figure 3 illustrates the parallelogram lift axle having dual tires at the each side, according to the present invention.
[019] Figure 4 illustrates details of the parallelogram lift axle, according to the present invention.
[020] Figure 5 illustrates assembly details of axle beam and transverse beam of the parallelogram lift axle, according to the present invention.
[021] Figure 6 illustrates the first hanger bracket, according to the present invention.

[022] Figure 7 illustrates the second hanger bracket, according to the present invention.
[023] Figure 8 illustrates the cross member, according to the present invention.
[024] Figure 9 illustrates the first air spring bracket, according to the present invention.
[025] Figure 10 illustrates the first top control arm assembly, according to the present invention.
[026] Figure 11 illustrates the first bottom control, according to the present invention.
[027] Figure 12 illustrates the center drop axle assembly, according to the present invention.
[028] Figure 13 illustrates the details of second air spring bracket along with the drop axle beam, according to the present invention.
[029] Figure 14 illustrates the first chassis jounce bracket, according to the present invention.
[030] Figure 15 illustrates the alignment bracket assembly with the second hanger bracket, according to the present invention.

[031] Figure 16 illustrates the details of the first and second alignment bracket, according to the present invention.
> [032] Figure 17 illustrates the first alignment bracket, according to the present invention,
[033] Figure 18 illustrates the details of the second alignment bracket, according to the present invention. )
[034] Figure 19 illustrates the rebound stopper chain assembly, according to the present invention.
[035] Figure 20 illustrates the rebound stopper chain bracket and i chain, according to the present invention.
Detailed description of the drawings:
[036] Figure 3 illustrates the heavy duty lift axle suspension system (13) fitted to the chassis frame (27) of the vehicle. The heavy duty lift axle suspension system (13) especially used as a pusher lift axle. It is a parallelogram type lift axle suspension system (13) having convolute type ride air springs (17) and dual tires on each side (28). It has higher ground clearance compared to the trailing arm type lift axle suspension (1). Moreover, it is first of its kind in world.

[037J Referring to Figure 4 and 5 of the accompanying drawing, the heavy duty lift axle suspension system (13), according to present invention, comprises: a pair of hanger brackets (namely, first hanger bracket (14A) and second hanger bracket (14B)), a pair of top control arm assemblies (namely, first top control arm assembly (15A) and second top control arm assembly (15B)), a pair of bottom control arm assemblies (namely, first bottom control arm assembly (16A) and second bottom control arm assembly (16B)), a pair of ride air springs (namely, first ride air spring (17A) and second ride air spring (17B)), a pair of lift air springs (namely, first lift air spring (18A)and second lift air spring (18B)), a pair of rebound chain assemblies (namely, first rebound chain assembly (19A) and second rebound chain assembly (19B)), a pair of jounce stopper assemblies (first jounce stopper assembly (20A) and second jounce stopper assembly (20B)), a pair of top air spring brackets (namely, first top air spring bracket (21 A) and second top air spring bracket (2IB)), eight pivots bolts and nuts (22), a centre drop axle assembly (23) having first air spring seating bracket and second air spring seating bracket, an alignment bracket assembly (24), a pair of frame jounce stopper (namely, first frame jounce stopper (25A) and second frame jounce stopper (25B)) and a pneumatic control system.
[038] The first hanger bracket (14A) and second hanger bracket (14B) are securely attached to the first side member of chassis frame (27A) and second side member of chassis frame (27B), respectively, using conventional bolts and nuts. The first top control arm assembly (15A) and first bottom control arm assembly (16A)are pivotally attached to

the first hanger bracket (14A) and the first air spring seating bracket (30A) of centre drop axle assembly (23) using the pivot bolts and nuts (22). The second top control arm assembly (15B) and second bottom control arm assembly (16B) are pivotally attached to the second hanger bracket (14B) and the second air spring bracket (30B)of centre drop axle assembly (23) using the pivot bolts and nuts(22).
[039j The first ride air spring (17A) is securely attached in between the first air spring bracket (30A) of centre drop axle assembly (23) and first top air spring bracket (21 A) attached to the first side member of chassis frame (27A). The second ride air spring (17A) is securely attached in between the second air spring bracket (30B) of centre drop axle assembly (23) and second top air spring bracket (21) attached to the second side member of chassis frame(27B). The first lift air spring (18A) is securely attached in between the first top control arm assembly (15A) and first bottom control arm assembly (16A). The second lift air spring (18B) is securely attached in between the second top control arm assembly (15B) and second bottom control arm assembly (16B).
[040] The first rebound stopper chain assembly (19A) is pivotally attached to the first side frame of chassis frame (27A) and first air spring bracket (30A) of centre drop axle assembly (23). The second rebound stopper chain assembly (19A) is pivotally attached to the second side frame of chassis frame (27B) and second air spring bracket (30B) of centre drop axle assembly (23).

[041] The first top control arm assembly (15A) is pivotally connected in-between top pivot through hole (33) of first hanger bracket (14A) and top pivot through hole (34) of air spring bracket seating bracket (30A) of center drop axle assembly (23). Similarly, first bottom control arm assembly (16A) is pivotally connected in-between bottom pivot through hole (35) of first hanger bracket (14A) and bottom pivot through hole (36A) of first air spring seating bracket (30A) of center drop axle assembly (23). As the control arm assemblies (15A&B, 16A&B) are made identical in length and shape, a parallelogram linkage is formed. The first lift air spring (18A) is attached in between the first top control arm assembly (15A) and first bottom control arm assembly (16A). That is, one end of the lift air spring is attached to the top control arm assembly and the other end is attached to the bottom control arm assembly. The first and second lift air springs (18A&B)) are inflated for actuating the parallelogram linkages. A lift force is exerted in both the top and bottom control arms (15A&B, 16A&B) while inflating the lift air springs (18A&B). Upon continuous lift force exerted in the control arms (15A&B, 16A&B), the parallelogram linkages are moved upward. The center drop axle assembly (23) is lifted- off from the road surface.
[042] A pair of rebound stoppers assemblies (19A&B) is provided between the center drop axle assembly (23) and the first and second side members of chassis frame (27A&B) of the vehicle. When the vehicle is operated, the center drop axle assembly (23) experiences a number of bumps or pot holes. When the center drop axle assembly (23) experiences a bump it moves upward towards the vehicle frame.

In order to negotiate this jerk caused by the bumps both the first and second ride air springs (17A&B) compress while the first and second lift air springs (18A&B) expand. On the other hand when a wheel of the vehicle falls on a pot hole in the road, the center drop axle assembly (23) moves downward relatively to the chassis frame. The both the first and second ride air springs (17A&B) expand simultaneously whereas both the first and second lift air springs (16A&B) compress. In order to limit over extension of ride air springs (17A&B), a pairs of rebound stopper chain assemblies (19A&B)) provided.
[043] The first and second jounce stopper assemblies (20A & 20B) maintain a desired gap between propeller shaft (not shown) of the vehicle and the centre drop axle assembly (23) is maintained while the centre drop axle assembly (23) lifting. The first and second rebound stopper chain assemblies (19A&B) limit the over travel of centre drop axle assembly (23) towards downward to prevent the over extension of first and second ride air springs (17&B). When lift the centre drop axle assembly (23), the first and second ride air springs (17A&B) are deflated and the first and second lift air springs (18A&B) are inflated using the pneumatic control system.
[044] Figure 6 illustrates the first hanger bracket (14A). It is rigidly attached to the first side frame of chassis frame (27A) of the vehicle by conventional means (i.e., bolts and nuts) and extended downwardly there-from. It has a pair of pivot through holes: first top pivot through hole (33A) and first bottom through hole (35A). The first top pivot

through hole (o>4A) and hrst bottom through holes (24) are used to connect the first top control arm (10) and the first bottom control arm (11) pivotally using the pivot bolts (24) and nuts. The first hanger bracket (14A) is made of conventional fabricating process. A special attention is given to design the first hanger bracket (14A). It has a high bending strength and torsion strength to withstand loads experienced in the heavy duty lift axle suspension system (13). The first hanger bracket (14A) has wide footprint on the chassis frame (27A) with multiples of holes (37A) which reduce magnitude of stress in the region of chassis frame (27A) where the first hanger bracket (14A) is attached.
[045] The first hanger bracket (14A) consists of first chassis L shaped plate (38), first L shaped side plate (39A), first support plate (40A), first main plate (41a), a circular pipe (42A), and a first square shaped spacer plate (43A), a first rectangular shaped spacer plate (44A) and three stiffeners (namely, first side straight stiffener (45A), first S shaped side stiffener (45B) and first S bent side stiffener (45C)). The first L shaped side plate (39A) and first support plate (40A) are welded apart with first main plate (41A). The first chassis L shaped plate (38A) is welded jointly with the first L shaped side plate (39A), first support plate (40A) and first main plate (41A). The first side straight stiffener (45A), and first S shaped side stiffener (45B) are welded to the first chassis L shaped plate (38A) and first L shaped side plate (39A). Similarly, first S bent side stiffener (45C) is welded with the first support plate (40A). The stiffeners (45A, B, & C) are provided to withstand a cornering load experienced in the first hanger bracket

(14A). Four slotted holes (49) are provided in the first main plate (41A). The slotted holes (49) are provided to connect the hanger to hanger cross member (29). In order to provide torsion strength the first circular pipe (42A) and first bottom stiffener (50A) are welded in-between the first L shaped side plate (39A) and the first support plate (40A). The first rectangular shaped spacer (44) and first square shaped washer (43) are welded to top side of the first chassis L shaped plate (38A).
[046] The second hanger bracket (14B) is rigidly attached to the second side frame of chassis frame (27B) of the vehicle by conventional means bolts and nuts and extended downwardly there¬from. It has a pair of pivot through slotted holes: second top pivot through slotted hole (33B) and second bottom through slotted hole (34B). The second top pivot through slotted hole (33B) and second bottom through slotted holes (34B) are used to connect the second top control arm assembly (15B) and the second bottom control arm assembly (16B) pivotally by the pivot bolts and nuts (22). The second hanger bracket (14B) is made of conventional fabricating process. A special attention is given to design the second hanger bracket (14B). It has a high bending strength and torsion strength to withstand loads experienced in the heavy duty lift axle suspension system (13). The second hanger bracket (14B,) has wide footprint on the chassis frame (27B) with multiples of holes (37B) which reduce magnitude of stress in the region of chassis frame (27B) where the second hanger bracket (14B) is attached.

[047] The second hanger bracket (14B) is shown in Figure 7. The second hanger bracket (14B) is structurally a mirror image of the first hanger bracket (14A) except the pair of pivot through slotted holes (33B; 34B) which are slotted shape holes. A alignment bracket assembly (namely inner alignment plate (52A) and outer alignment plate (52B)) is attached to the slotted holes along with the second top and second bottom control arms assembly. Four slotted holes (26) are provided in the second main plate (4IB). The slotted holes (26) are provided to connect the hanger to hanger cross member (29).
[048] Figure 8 illustrates the hanger to hanger cross member (29). The hanger to hanger cross member (29) is a C shaped plate (48). The hanger to hanger cross member (29) is connected in between the first and second hanger bracket assemblies (14A and 14B) attached with both sides of chassis frame (27A & 27B) through four holes (55) provided at the each end of the C shaped plate (48). In order to reduce mass of the hanger to hanger cross member (29) four relief holes (56) are provided. The hanger to hanger cross member (29) provided to withstand the cornering load experienced in the first and second hanger bracket (14A& B).
[049] Figure 9 illustrates the first air spring bracket (21A). The first air spring bracket (21 A) is rigidly attached to the first side frame of chassis frame (27A) of the vehicle by conventional means. The first air spring bracket (21 A) is used to hold the first ride air spring (17A) with side frame of chassis frame (27A). The first air spring bracket (17A) consists of a first bottom flat plate (57), a first spacer plate (58) and

first C shaped plate (59). The first C shaped plate (59) is welded with the first bottom flat plate (57) vertically. The first bottom flat plate (57) has two holes (60). The holes (60) are provided to attach the first ride air spring (17A). The first spacer plate (58) is welded on the first bottom flat plate (57). The first C shaped plate (59) has multiple holes (61). The holes (61) are provided to clamp the first air spring bracket (21A) to the side frame of chassis frame (27A).
[050] The second air spring bracket (2 IB) is structurally mirror image of the first air spring bracket (21 A). It is rigidly attached to the side frame of chassis frame (27B) of the vehicle by conventional means. The second air spring bracket (2 IB) is used to hold the second ride air spring (17B) with side frame of chassis frame (27B).
[051] Figure 10 illustrates the first top control arm assembly (15A). The second top control arm assembly (15B) is mirror image (symmetric object) of the first top control arm assembly (15A). The first top control arm assembly (15A) comprises a control arm (62), a circular sleeve (63), a pairs of wear pads (64) and a polyurethane bush (PUbush, 65).
[052] Figure 11 illustrates the first top control arm (62). The front pivotal portion of the control arm (66 A) has hollowing cylindrical profile for providing pivotal linkage with the hanger brackets (14A), a rear pivotal portion control arm (66B) having hollow cylindrical profile for providing pivotal linkage with said center drop axle assembly (23), and an intermediate load bearing portion of control arm (67) having hollow rectangular profile. The front pivotal portion (66A) and the rear

pivotal portion (66B) of control arm (15A) are also known as "eyes" of the control arm (15A). The load bearing portion (67) is formed by welding four plates (i.e., Top bent plate (67A), bottom bent plate (67B), first side cover plate (67C) and second side cover plate (67D)). The four : plates (67 A,B,C&D) are rigidly welded together. The eyes (66A& B) are welded at both the load bearing portion (67). A flat lever plate (68) is welded with the intermediate load bearing portion (67) of the first top control arm (15A). In order to the bending strength of flat lever plate (68), three stiffeners (69) are welded at back side. Three holes (70) are provided in the flat lever bracket (68). The holes (70) are provided to the flat lever bracket (68) to attach the first lift air spring (18A) by conventional mechanical means. The C shaped rebound stopper plate (71) is welded at the one end of the flat lever bracket (68). It is a special feature of metal-to-metal rebound stopper provided in the present invention. If first rebound stopper chain assembly (19A) fails, the C shaped rebound stopper plate (71) of top control arm assembly (15A) engages to the C shaped rebound stopper plate (71) of bottom control arm assembly (16A) when the axle moves downward ( at the time of axle experiences a big pot hole). Thereby, over extension of first ride air spring (17A) is limited (details are given in the proceeding paragraphs). A pairs of cylindrical shape PU bush (65) is inserted into both the eyes (66A&B)) of the first top control arm assembly. A pairs of circular sleeves (63) is inserted into both the PU bushes (65 A&B) inserted into the pivotal portions (i.e., eyes, 66A&B). The first bottom control arm assembly and second bottom control arm assembly are same as first top control arm assembly and second top control arm assembly respectively.

[053] Figure 12 illustrates the center drop axle assembly (23). A special attention is given to the design of the center drop axle assembly (23). The center drop axle assembly (23) consists of an axle beam (74) (having box section and a drop at center), a first air spring seating bracket (30A) and a second air spring seating bracket (30B). The air spring seating brackets (30A&B) are made of fabrication process. The air spring brackets (30A&B) are welded apart to the axle beam (74) of center drop axle assembly (23). The second air spring seating bracket (30B) is structurally symmetric object of the (i.e., mirror image) first air spring seating bracket (30A). The air spring seating brackets ((30A&B) are provided to hold the ride air springs (17A&B) rigidly (at bottom side).
[054] The first air spring seating bracket (30A) consists of two vertical plates, namely first and second vertical plates (75A&B)), a first top Z shaped plate (76), a pair of L shaped brackets (namely, first L shaped bracket (77A) and second L shaped bracket (77B)), a first guide plate 78A), a pair of guide pins (79) and a pair of two identical stiffeners (80), a inner stiffener (81), a pair of rebound stopper plates (82), a circular tube (83) and bottom C shaped bracket (84). The first top Z shaped bracket (76A) and first bottom C shaped bracket (84) are welded to the axle beam (74) at top side and bottom side, respectively. The vertical plates (75A&B) ) are welded apart to the axle beam (74) and the first top Z shaped plate (76). Similarly, the stiffer plates (80) are also welded apart to the axle beam (74) at the bottom side of the first top Z shaped bracket (76A). The first top Z shaped bracket (76A)

has three holes (85); which are used attach the first ride air spring (17). The circular tube (83) is welded in between the two vertical plates (75). The first L shaped plate (77A) is welded at the bottom side of both the two vertical plates (75A). The second L shaped plate (77B) is welded at the bottom side of the first and second vertical plates (75B). A pair of guide pins (79) is welded at the top side of first top Z shaped plate (76A). The guide plate (78) is also welded at the top side of first top Z shaped plate (76A). It is used to hold a nylon wear pad or PU sheet (detail provided in proceeding paragraphs). The identical rebound stopper plates (82) are welded apart with the first L shaped bracket (77B). The rebound stoppers (82) have holes which are used to hold the rebound stopper chain assembly (19A).
[055] Figure 13 illustrates the second jounce stopper assembly (20B). The first jounce stopper assembly (20A) is exactly similar to second jounce stopper assembly (20B). The second jounce stopper assembly (20B) consists of a nylon wear pad (86), a pair of washers (87) and a pair of either dowel pins or split pins (88). The nylon wear pad (86) has two holes. The holes are used to assemble the nylon wear pad (86) with guide pins (79) of the center drop axle assembly (23). The nylon wear pad (86) is secured to the guide pins (79) using the washers (87) and dowel pins or split pins {88). The second jounce stopper assembly is securely attached to the second air spring seating bracket of centre drop axle assembly. The first and second jounce stoppers assemblies are used to limit the upper dynamic travel height of the lift axle suspension when it is operated in undulated roads.

[056] Figure 14 illustrates the first chassis jounce stopper bracket (25A). It consists of an L shaped plate (89) and a pair of stiffener plates, namely, first stiffener plate (31) and second stiffer plate (32). The L shaped plate (89) has six holes (90). They are provided to attach the bracket (25A) with the chassis side frame (27A). In order to reduce the mass, two circular reliefs (91) are provided. The second chassis jounce stopper bracket (25B) is structurally similar to the first chassis jounce stopper bracket (25A). The first chassis jounce stopper bracket (25A) and first chassis jounce stopper bracket (25B) are securely attached to the chassis frame (27&B) just above the center drop axle assembly (23) where the nylon wear pads (86) come to contact with the chassis frame bottom when the center drop axle assembly (23) is lifted.
[057] Figure 15 illustrates the alignment bracket assembly (24) along with the second hanger bracket (14B). The main requirement is that both the top and bottom control arm assemblies (15A&B, 16A&B) should be adjusted simultaneously in fore and apt directions (at the same equal distance). Therefore, a special attention is given to design the simple and unique alignment bracket assembly (24). The alignment bracket assembly (24) consists of inner alignment bracket (52), outer alignment bracket (53), three screws (46), three alignment nuts (47) and three lock nuts ((51), two lock nuts are not visible)). The inner alignment bracket (52) has two holes (91) and the outer alignment bracket (53) has two holes (92). The inner alignment bracket (52) and outer alignment bracket (53) are attached to the second hanger bracket (14B) respectively along with the pivots bolts

(22). The both inner alignment bracket (52) bracket and outer alignment bracket (53) slide along with a pair of pivot bolts (22) in the fore and apt directions (while performing alignment in the axle). When axle alignment is carried out, the screws (46) are rotated to position the axle in the de sired location. After alignment procedure is completed, the lock nuts (three lock nuts (47)) are tightened with required torque to prevent the nut loosening.
[058] Figurel6 illustrates the inner alignment bracket (52) and outer alignment bracket (53). The inner alignment bracket is a nut and screw mechanism (i.e., similar to conventional screw jack mechanism). The inner alignment bracket (52) is a nut and screw mechanism and the outer alignment bracket (53) is a pair of nuts and screws mechanism. The inner alignment bracket (52) and outer alignment bracket (53) are used to move both the second top and second bottom controls arms (15B,16B) in fore and apt direction.
[059] Figure 17 illustrates the details of outer alignment bracket (53), according to the present invention. It is used to adjust the control arms (1533, 16B) at the initial process (i.e., control arms positioned process) of the axle alignment. It consists of a main alignment plate (54), a front cover plate (72), a rear cover plate (73), and a nut position plate (107) and a pair of nuts (108). The nut position plate (107) is used to position the nuts (108) at a desired position in the main alignment plate (54). The front cover plate (72), rear cover plate (73) are used to accommodate the nuts (108) within the nut position plate (70). The main alignment plate (54) has pair of holes (92) which are

used to attach it with the second hanger bracket (14B) at front side. The front cover plate (72) which has a pair of holes (109) is welded with the main alignment plate (54). The front cover plate (72) is positioned along with the nuts (108) which are aligned with the holes (109) of front cover plate (72) and welded together with the main alignment plate (54) and front cover plate (72). The rear cover plate (73) has a pair of holes (110) is aligned with the nuts (108) and welded the main alignment plate (54) and the rear cover plate (72).
[060] Figure 18 illustrates the details of inner alignment bracket (52), according to the present invention. It is used to adjust the control arms (15B, 16B) at the final process (i.e., control arms tightening process) of the axle alignment. It consists of a main alignment plate (93), a front cover plate (94), a rear cover plate (95), and a nut position plate (96) and a nut (97). The nut position plate (96) is used to position the nut (97) at a desired position in the main alignment plate (93). The front cover plate (94), rear cover plate (95) are used to accommodate the nuts (97) within the nut position plate (96). The main alignment plate (93) has pair of holes (91) which are used to attach it with the second hanger bracket (at rear side). The front cover plate (95) is welded with the main alignment plate (94) which has a hole at center (98). The front cover plate (95) is positioned along with the nut (97) which is aligned with the hole (98) of front cover plate and welded together with the main alignment plate (93) and front cover plate (94). The rear cover plate (95) has a hole (106) is aligned with the nuts (97) and welded the main alignment plate (93) and the rear cover plate (95).

[061] Figure 19 illustrates the first rebound chain assembly (19A). It consists of a chain (99), a chain bracket (100) and a bolts and nuts (101). Figure 20 illustrates the chain bracket (100). The chain bracket (100) is made of fabrication process. It is made of two identical L shaped plates (102). It is welded apart using a spacer disk plate (103). The together L shaped plates (102) have multiples holes (104) which are used to attach the bracket with the chassis side frame (27A). Each L shaped plate (102) has through hole (105). It is used to connect the chain (99) with the chain bracket (100) using the bolts and nuts (101).
[062] The heavy duty lift axle suspension system (13) is designed for lowering the center drop axle assembly (23) to road surface for sharing the load and raising the center drop axle assembly (23) to a required distance from the road surface when the vehicle is operating in unladen condition. Under lifted condition, the axle should be stably retained in position; so that advertent road surface contact is prevented even when the tires experience bumps or pot holes. This heavy duty lift axle suspension system (13) aims at extending tire life and reducing fuel consumption because the center drop axle assembly (23) can be lifted when reversing or when not need the axle.
[063] In order to lift and lower a pneumatic control system is used. It is not a part of present invention. Therefore, all the details are not given. It consists of direction control valves, pressure gauge, control box and electrical switch. The control system provides required air to the ride air springs (17A&B) during normal operation of the vehicle.

When the lift axle (13) is not required, such as the situation that when the vehicle is operated with partially loaded condition or vehicle is operated in empty condition, the vehicle control system deflates the ride air spring (17 A&B) and inflates the lift air springs (16A&B). ; Therefore, the top control arm assemblies (15A&B) and bottom control arm assemblies (16A&B) are rotated counter clockwise about the pivotal points (22). Thereby, the center drop axle assembly (23) is moved vertically upward and the center drop axle assembly (23) is held in position by lift air springs (16A&B) i.e., the center drop axle assembly (23) is lifted off from the road surface and maintained at required distance from the road surface.
[064] A unique of the present invention is the parallelogram mechanism used in the non-steer lift axle which has dual tires (28) the each end of the center drop axle assembly (23). The parallelogram mechanism maintains a required higher ground clearance in the lift axle system compared to the commercial available trailing arm type lift axle suspension (Figure 1). Especially, distance between the brake chambers (one of safety critical parts of the vehicle) to road surface is increased remarkably. The brake chambers will not affect when the vehicle experiences big hump. Therefore, the lift axle can be used in the heavy duty MAV operated in the developing countries.
[065] In addition, the parallelogram mechanism maintains a uniform distance in between the top and bottom bead plates of both the lift air springs (18A&B) and ride air springs (17A&B). Therefore, bead plates are subjected to compressive load. The fasteners of the air springs

(17A&B and 18A&B) are subjected to tensile load and shear load. As the parallelogram mechanism used in the center drop axle assembly (23), the life of the ride air springs (17A&B) extended and premature failure of air spring's bead plates and rubber bellows griming failures are prevented.
[066] Another unique of the present invention is the design of the top and bottom control arms (15A&B, 16A&B). Compact control arms (15A&B, 16A&B)) are provided. The bottom control arms (16A&B)) and top control arms (15A&B) are similar to each others. In order to limit the rebound the axle, a metal to metal stopper (i.e., C shaped rebound stopper 71) is designed. When the axle experiences a pot hole, the axle travels downward direction. Therefore the top and bottom control arms (15A&B, 16A&B) also move downward. The C shaped stopper plate (71) of the top control arms (15A&B) engages the C shaped stopper plate (71) of the bottom control arms (16A&B). Thereby, the rebound travel of the axle is limited.
[067] Another unique of the present invention is using the conventional convolute type ride air springs (17A&B) in the heavy duty lift axle suspension(13) having dual tires (28). The convolute type ride air springs (17A&B) are more suitable to the vehicle operated in mud road and undulated toad. Therefore, premature failure due to rubbing action of debris, which was observed in the reversible sleeve air spring, is prevented. Thereby the desirable durability of the lift axle system is achieved. In addition, the ride air springs (17A&B) consume low amount of compressed air. Therefore, conventional small capacity

of compressor is sufficient. Thereby, load cost, less power engine and high mileage vehicle is provided according to one of the objectives of present invention.
[068] Yet uniqueness of the present invention is the use of less packaging area to mount the lift axle air suspension system (13) in the chassis frame (27 A&B). As the lift air springs (18A&B) are packaged within the top and bottom control arms (15A&B, 16A&B), the suspension system can be fitted in the pusher location (i.e., in-front of drive axle) of a rigid truck where a limited package area is available. Similarly, it can also be fitted in the pusher location of the tractor vehicle which has limited package area at the rear end of the vehicle.
[069] Another uniqueness of the present invention is the design of simple alignment bracket assembly (24). The present invention provides a unique and simple alignment bracket assembly (24). When axle alignment is performed, both the second top control arm (15B) and second bottom control arm (16B) can be easily moved fore and apt directions using the unique alignment bracket assembly (24).
[070] The present invention is first of its kind in world. It is a parallelogram type lift axle suspension disclosed to lift the non-steer axle having dual tires at both sides. 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.

1. A heavy duty lift axle suspension system (13) comprises:
- a pair of hanger brackets (14A and 14B), the first hanger bracket (14A) secured to a first side member (27A) of chassis frame and the second hanger bracket (14B) secured to a second side member (27B) of the chassis frame;
- a hanger to hanger cross member (29) connected in between the hanger brackets (14A) and (14B);
- a center drop axle assembly (23); having a first air spring seating bracket (30A), a second air spring seating bracket (30B) and axle beam (74) having box section and a drop at center;
- a pair of top control arm assemblies (15A and 15 B); the first top control arm assembly (15A), pivotally connected in between the first hanger bracket (14A) and the first air spring seating bracket (30A) of the center drop axle assembly (23) using a pair of pivot bolts and the second top control arm assembly (15B) , pivotally connected in between the second hanger bracket (14B) and the second air spring seating bracket (30B) of the center drop axle assembly (23) using a pair of pivot bolts;
- a pair of bottom control arm assemblies; the first bottom control arm assembly (16 A), pivotally connected in between the first hanger bracket (14A) and the first air spring seating bracket (30A) of the center drop axle

assembly (23) by pivot bolts and the second bottom control arm assembly (16B), pivotally connected in between the second hanger bracket (14B) and second air spring seating bracket (30B) of the center drop axle assembly (23) by pivot bolts;
- a pair of air spring brackets; first top air spring bracket (21 A), attached to the first side member (27A) of the chassis frame above the centre drop axle assembly (23) and the second air spring seating bracket (30B)3 attached to the second side member (27B) of the chassis frame above the centre drop axle assembly (23);
- a pair of ride air springs; the first ride air spring (17A), attached in between the first air spring seating bracket (30A) of the center drop axle assembly (23) and the first top air spring bracket (21 A) and second ride air spring (17B), attached in between the second air spring seating bracket (30B) of the center drop axle assembly (23) and second top air spring brackets (2IB);
- a pair of lift air springs (18A and 18B); the first lift air spring (18A), attached in between first top control arm assembly (15A) and first bottom control arm assembly (16A) and the second lift air spring (18B), attached in between the second top control arm assembly (15B) and the second bottom control arm assembly (16B);
- a pair of rebound stopper chain assemblies (19A and 19B); the first rebound stopper chain assembly (19A), connected in between the first side member (27A) of the chassis

frame and the first air spring seating bracket (30A) of the center drop axle assembly (23) and the second rebound stopper chain assembly (19B), connected in between the second side member (27B) of the chassis frame and the second air spring seating bracket (30B) of the center drop axle assembly (23);
- an alignment bracket assembly (24), connected with the second hanger bracket (14B) using pivot bolts (22);
- a pair of chassis frame jounce stopper brackets (25A and 25B); the first chassis frame rebound stopper bracket (25A), attached to the first side member (27A) of the chassis frame and second chassis frame rebound stopper bracket (25B), attached to the second side member (27B) of the chassis frame where the axle beam (74) comes to contact when the center drop axle beam assembly (23) is lifted.
2. The heavy duty lift axle suspension system (13) as claimed in claim 1, wherein said first top control arm assembly (15A), which is structurally mirror images of the second top control arm assembly (15B), comprises:
- first top control arm (62);
- four wear pads (64); made of nylatron or nylon 6
- a pair of sleeve (63); and
- a pair of polyurethane (PU jbushes (65).

3. The heavy duty lift axle suspension system (13) as claimed in
claim 1, wherein said first bottom control arm assembly (16A),
which is structurally mirror images of the second top control
arm assembly (16B), comprises:
- first bottom control arm (73);
- four wear pads (64); made of nylatron or nylon 6
- a pair sleeve (63); and
- a pair polyurethane (PU )bushes (65)
4. The heavy duty lift axle suspension system (13) as claimed in
claim 2, wherein said first top control arm (62) comprises:
- a front pivotal portion (66A), having hollow cylindrical profile for providing pivotal linkage with said center drop axle assembly (23);
- a rear pivotal portion (66B), having hollow cylindrical profile for providing pivotal linkage with said hanger bracket (14A);
- an intermediate load bearing portion (67);
- a lever bracket (68) , welded with said intermediate load bearing portion (67) for providing linkage with the first lift air spring (18A), and
- a metal to metal rebound stopper, welded with said lever bracket (68).
5. The heavy duty lift axle suspension system (13) as claimed in
claim 3, wherein said first bottom control arm (73) comprises:

- a front pivotal portion (66A), having hollow cylindrical profile for providing pivotal linkage with said center drop axle assembly (23);
- a rear pivotal portion (66B), having hollow cylindrical profile for providing pivotal linkage with said hanger bracket (14A);
- an intermediate load bearing portion (67) ;
- a lever bracket (68) welded with said intermediate load bearing portion (67) for providing linkage with first lift air spring (18A),
- a metal to metal rebound stopper having rebound stopper (71), welded with said lever bracket (68), and
- a transverse rod guide hole (72), provided to attach the transverse rod assembly (26) for withstanding a high cornering load.
6. The heavy duty lift axle suspension system (13) as claimed in claim 1, wherein said center drop axle assembly (23), comprises the first air spring seating bracket (30A); the second air spring seating bracket (30B); and the axle beam (74), is pivotally connected to said hanger brackets (14A &B) through said controls arm assemblies (the first top control arm assembly (15A), the second top control arm assembly (15B), the first bottom control arm assembly (16A) and the second top control arm assembly (16B)) and said pivot bolts .

7. The heavy duty lift axle suspension system (13) as claimed in claim 1, wherein said first lift air spring (18A) is connected in between the first top control arm assembly (15A) and the first bottom control arm assembly (16A) and the second lift air spring (18B) is connected in between the second top control arm assembly (16B) and the second bottom control arm assembly (16B).
8. The heavy duty lift axle suspension system (13) as claimed in claim 1, wherein said first ride air spring (17A) is connected in between the first top air spring bracket (21A) and the first air spring seating bracket (30A) of the center drop axle assemble (23) and the second ride air spring (17B) is connected in between the second top air spring bracket (2IB) and the second air spring seating bracket (30B) of the center drop axle assembly (23).
9. The heavy duty lift axle suspension system (13) as claimed in claim 1, wherein said first hanger bracket (14A), which is structurally symmetric part of second hanger bracket (14B) except the slotted holes (33B and 35B), comprises :

- first main plate (41A), having multiple slotted holes (49A) to connect the hanger to hanger cross member (29);
- first chassis L shaped plate (38A), having multiple holes (37A) to attach to the first side member (27A) of chassis frame;

- first L shaped side plate (39a), welded with the first chassis L shaped plate (38A); having pivot holes (33A,35A) for connecting the first top control arm assembly (15A) and the first bottom control arm assembly (15A) pivotally;
- first support plate (40A), welded with said first chassis L shaped plate (38A), having pivot holes (33A,35A) for connecting the first top control arm assembly (15A) and first bottom control arm assembly (16A) pivotally;
- a circular pipe (42A), welded in between the first chassis L shaped plate (38A) and the first support plate (40A);
- a first spacer plate (44A), welded to the first chassis L shaped plate (38A).
- a first square shaped spacer plate (43A), welded on the and first chassis L shaped plate (38A); and
- a plurality of multiple stiffeners (45A, 45B, 45C).
10. The heavy dutylift axle suspension system (13) as claimed
in claim 1, wherein each said axle alignment bracket assembly (24) comprises:
- an inner alignment bracket (53), having a pair of nuts which is rigidly accommodated at a part, to position the control arms (15B and 16B) with the second hanger bracket (14B) at a desired position quickly and to perform alignment at initial stage of axle alignment process;
- an outer alignment bracket (52), having a nut which is rigidly accommodated at the center, to position the control arm's (15B and 16B) with the second hanger bracket (14B) at a

desired position quickly to perform perfect holding at final stage of the axle alignment process;
- screws (46.) to adjust the position of the inner alignment bracket (52), and the outer alignment bracket (53), during the axle alignment process;
- nuts (47) to maintain the position of the screws (46) with the second hanger bracket (14B); and
lock nuts (51) to lock the position of the inner alignment bracket (52), and the outer alignment bracket (53), at the final stage of the axle alignment process;
11. The heavy dutylift axle suspension system (13) as claimed
in claim 1, wherein said first rebound stopper chain assembly
(19A), which is structurally similar to said second rebound
stopper chain assembly (19B) , is comprised of:
- a chain bracket (100) made of two plates (102) rigidly connected;
- a chain (99), pivotally connected the chain bracket (100) to the first air 'spring seating bracket (30A) of the center drop axle assembly (23);
12. The heavy duty lift axle suspension system (13) as claimed
in claim 1, wherein the first top air spring bracket (21 A) is
comprised of;
- a circular plate (57), having holes (60) to secure the first ride air spring (17A); a spacer plate (58), welded on said circular plate (57),

- an plate (61), secured to the first ride air spring (17A) and the first side member (27a) of the chassis frame of the vehicle.
13. The heavy duty lift axle suspension system (13) as claimed
in claim 1, wherein said first jounce stopper assembly (20A) which is similar to second jounce stopper assembly (20B), comprises :
- a first nylon wear pad (86), attached to the first air spring seating bracket (30A) of the center drop axle assembly (23);
- washers (87), provided to maintain a high pressure on said first nylon wear pad (86).
- dowel pins (88) provided to clamp the nylon wear pad (86) with the guide pins (79) of the center drop axle assembly (23).
14. The heavy duty lift axle suspension system (13) as claimed in claim 1, wherein said first chassis jounce stopper bracket (25A), which is similar to the second chassis jounce stopper bracket (25B), is comprised of;
-a L shaped plate (89), having holes (90) to secure with the first side member (27A) of the chassis frame; and
- a pair of stiffener plates (31, 32) welded on said L shaped plate (89).