TECHNICAL FIELD
[0001] The present subject matter relates to a step through vehicle. More particularly, the present subject matter relates to the main tube structure.
BACKGROUND
[0002] In automobiles, the chassis of the vehicle consists of the frame, suspension, wheels and brakes. The chassis sets the overall style of the vehicle. The frame must be torsion resistant so that the frame should not buckle on uneven road surfaces and any distortion should not be transmitted to the body.
[0003] Generally, in a two-wheeled or three-wheeled vehicle with a frame assembly, the frame assembly extends in longitudinal direction of the vehicle. The frame assembly acts as'a structural member and load-bearing member of the vehicle. Also, the drive wheel and the driven wheel are supported by the frame assembly. In a saddle-ride type vehicle, the power unit either is mounted or is low-slung to the frame assembly. Generally, the wheels are connected to the frame through damping members. Moreover, in a vehicle with a step-through type portion, the power unit is swingably mounted to the frame assembly through the damping members, which are typically suspensions. Therefore, the forces acting on the frame assembly is high due to added weight of the power unit on the rear portion. The suspension plays an

essential role in damping the forces acting on the wheels and forces from the
power unit from reaching the frame assembly.
BRIEF DESCRIPTION OFTHE DRAWINGS [0004] The detailed description is described with reference to the
accompanying figures. The same numbers are used throughout the drawings
to reference like features and components. [0005] Fig.l is a side view of a step through type vehicle as per one
embodiment ofthe present invention.
[0006] Fig.2 is a perspective view of a frame assembly as per one
embodiment ofthe present invention [0007] Fig.3 is the enlarged view of the frame assembly as per one
embodiment ofthe present invention, [0008] Fig. 4 is the exploded view of the frame assembly as per one
embodiment ofthe present invention. [0009] Fig. 4a is the sectional view ofthe gusset main tube bottom as per one
embodiment ofthe present invention.
DETAILED DESCRIPTION [00010] Typically, in step-through type vehicle the frame assembly includes
the front zone and rear zone. Typically, in vehicles with a step-through type
portion the frame assembly includes a front zone and a rear zone. The front
zone supports the steering assembly along with the front suspension of the

vehicle. The front zone includes a main tube that provides stiffness and strength for withstanding the forces acting thereon. The rear zone includes a sub-frame that supports the vehicle parts including power unit along with the power train, the rear wheel, and the rear suspension connected thereof. Therefore, the rear zone and front zone is subject to various forces from the rear wheel through the suspension and from the power unit and from the front wheel. Further, the impacts from the road like bumps and vibration from the power unit are also acting on the frame assembly. Moreover, the vehicle is provided with utility and style parts that are mounted to the frame assembly for providing utility space and aesthetic appeal, which are to be mounted with minimal variations. [00011] To this end, the various vehicle parts like rear suspension, utility box being mounted to the rear zone of the frame assembly requires multiple brackets that are welded to the frame assembly. Moreover, provision of multiple brackets requires multiple welding, which increases stress concentration and also reducing the strength at that particular point at that local region. Further, multiple welding in close vicinity results in dimensional variations of the frame assembly affecting the assembly/mounting of components thereat. Moreover, dimensional variation of the frame assembly affects the mounting position of the components. As the parts like floorboard, utility box are rigid parts having fixed mounting points, the aforementioned

variations will lead to interference or gaps between the parts. As such, the hard points are subject to various forces and any dimensional variations at the hard points, which are the essential load bearing points, will further affect the strength at the particular point. The riding characters of the vehicle area is compromised as the variation may affect the orientation of mounting of the vehicle parts. This affects the riding characteristics of the vehicle as functional characteristics of the suspension are changed due to improper orientation or alignment. Moreover, the suspension is mounted to a single member of the frame assembly. Therefore, such variations affect the life of the frame assembly as the hard points are subject to forces resulting in failure due to the forces acting on the single member.
[00012] In addition, any dimensional variations in the frame assembly will affect the layout thereby disturbing the mounting of parts of the vehicle. Therefore, the mounting of the adjoining parts like seat assembly, the style panels, the floorboard for load carrying are affected resulting in poor fit and finish of the vehicle resulting in poor aesthetics.
[00013] Further, the durability of the step through vehicle depends on the main tube which starts from the head tube to cross tube floor board which is at the center of the frame. The main tube projected vertically down from head tube and takes a bend at acute angle extends to vehicle rear wheel direction and joins with frame middle structure that is cross tube floorboard.

[00014] Further, when the main tube is bend at acute angle, maintaining the consistency in the bend and dimensional requirement and quality is tough, as the bending of main tube will led to deformation of shape due to stress applied at each joint and developed wrinkles at the joint. Further, this affects the durability of the frames. The thickness in the bend region of the main tube is inconsistent, which affects the strength and durability of the main tube. Further, in the known art, the flat shaped support plate and the down frame and reinforcing plate are joined to support plate, which increases the number of components used and increases the cost and weight of the vehicle. Further, this is not feasible for the low cost vehicle.
[00015] Therefore, there is a need to have an improved main tube structure which overcomes all of the above problems and other problems known in art.
[00016] The present subject matter discloses a main tube structure to ensure the stable mounting of the main tube frame and also, improve durability, decrease weight of the vehicle.
[00017] As per one aspect of present invention, the frame assembly divided into the two parts namely; main tube top and main tube bottom. Further, as per one aspect of the present invention, the frame assembly includes the main tube and pair of rear tube extends inclinedly rearward from a rear portion of the main tube defining a step through portion and the projected portion, which is mounted to the pair of rear tubes and the main tube, ensures the additional

space for the luggage carrier. As per one aspect of present invention, the cross member termed as rear bridge structure connects the pair of rear tubes. Further, as per one aspect of the present invention, main tube is mounted to the head tube of the vehicle and extends downwardly where the floorboard tube is welded to the main tube of the vehicle. Further, as per one aspect of the present invention, the cross tube floorboard is mounted in between the pair of floorboard tube to provide the strength to the mounting of floorboard tube.
[00018] Further, as per one aspect of the present invention, the main tube top is mounted to the head tube and main tube bottom is mounted to the main tube top and extends inclinedly to the cross tube floorboard, ensures the strength to the mounting of the main tube bottom. As per one aspect of the present invention, the main tube top is mounted to the head tube with the gusset main tube top and the gusset main tube top acts as the bridge between the main tube top and head tube, thereby, provides additional strength to the mounting of the main tube top and shares the load applied on the frame assembly.
[00019J Further, as per one aspect of the present invention, the main tube bottom is mounted to the main tube top by having an abut joining and the gusset main tube bottom is mounted in between the main tube top and main tube bottom, ensures the strength and stiffness to the frame assembly.
[00020] Further, as per one aspect of the present invention, the main tube bottom is mounted with the main tube top at a predetermined angle A.

Further, as per one embodiment of the present invention, the predetermined angle is 90 degrees with respect to the vertical axis, ensures the distribution of the load on the frame assembly. Further, as per one aspect of the present invention, the main tube top and main tube bottom is further supported by the gusset main tube bottom, ensures the strength and durability of the welded joint at 90 degrees. Further as per one aspect of the present invention, the gusset main tube bottom and main tube bottom have mounting holes, where the floor board tubes are mounted in the mounting holes of the gusset main tube bottom and main tube bottom, ensures the strength of the frame assembly.
[00021] Further, as per one aspect of the present invention, the support member like gusset main tube top, main tube bottom etc. is either selectively welded or continuous welding with the member and main tube of the frame assembly. It is a feature that the need for multiple welding for multiple brackets are reduced whereby deformation of the frame assembly is also reduced. It is an additional feature that the required distance between various hard points of the frame assembly are retained. It is an additional feature that the ride characteristics are improved.
[00022] The various other features of the invention are described in detail below with reference to the accompanying drawings. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or

structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the corresponding reference number. With reference to the accompanying drawings, wherein the same reference numerals will be used to identify the same or similar elements throughout the several views.
[00023] Further "front" and "rear", and "left" and "right" referred to in the ensuring description of the illustrated embodiment refer to front and rear, and left and right directions as seen in a state of being seated on a seat of the saddle type vehicle. Furthermore, a longitudinal axis refers to a front to rear axis relative to the vehicle, while a lateral axis refers to a side to side, or left to right axis relative to the vehicle. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.
[00024] Fig. 1 illustrates a left side view of a step through vehicle ("the vehicle") 100, in accordance with an embodiment of the present subject matter. The vehicle (100) illustrated, has a frame assembly (105). The frame assembly (105) includes a head tube (105A), a main frame assembly (105B). One or more suspensions (110) connect a front wheel (115) to a handlebar assembly (120), which forms the steering assembly of the vehicle (100). The steering assembly is rotatably disposed through the head tube (105A). The main frame assembly (105B) extends rearwardly downward from the head

tube (105A) and includes a bent portion thereafter extending substantially in a longitudinal direction. Further, the frame assembly (105) includes one or more rear tubes (105C) extending inclinedly rearward from a rear portion of the main frame assembly (105B) towards a rear portion of the vehicle (100).
[00025] The vehicle (100) includes a power unit (125) comprising at least one of an internal combustion (IC) engine (125) and a traction motor (135). For example, the traction motor (135) is a brush less direct current (BLDC) motor. The power unit is coupled to the rear wheel (145). In one embodiment, the IC engine (125) is swingably connected to the frame assembly (105). In the present embodiment, the IC engine (125) is mounted to the swing arm (140) and the swing arm (140) is swingably connected to the frame assembly (105). The traction motor (135), in one embodiment, is disposed adjacent to the IC engine (125). In the present embodiment, the traction motor 135 is hub mounted to the rear wheel (145). Further, the vehicle (100) includes a transmission means (130) coupling the rear wheel (145) to the power unit. The transmission means (130) includes a continuously variable transmission, an automatic transmission, or a fixed ratio transmission. A seat assembly (150) is disposed above the power unit and is supported by the rear tubes (105C) of the frame assembly (105). In the present embodiment, the seat assembly (150) is hingedly openable. The frame assembly (105) defines a step-through portion ST ahead of the seat assembly (150). A floorboard (155)

is disposed at the step-through portion, wherein a rider can operate the vehicle 100 in a seated position by resting feet on the floorboard (155). Further, the floorboard (155) is capable of carrying loads.
[00026] The vehicle includes an on-board battery (not shown) that drives the traction motor (135). Further, the frame assembly (105) is covered by plurality of body panels including a front panel (160A), a leg shield (160B), an under-seat cover (160C), and a left and a right side panel (160D), mounted on the frame assembly (105) and covering the frame assembly (105) and parts mounted thereof.
(00027) In addition, a front fender (165) is covering at least a portion of the front wheel (115). In the present embodiment, the front fender (165) is integrated with the front panel (160A). A utility box (not shown) is disposed below the seat assembly (150) and is supported by the frame assembly (105). A fuel tank (not shown) is disposed adjacently to the utility box (not shown). A rear fender (175) is covering at least a portion of the rear wheel (145) and is positioned below the fuel tank and upwardly of the rear wheel (145). One or more suspension(s) (180) are provided in the rear portion of the vehicle (100) for connecting the swing' arm (140) and the rear wheel (145) to the frame assembly (105) for damping the forces from the wheel (145) and the power unit from reaching the frame assembly (105).

[00028] Furthermore, the vehicle (100) comprises of plurality of electrical
and electronic components including a headlight (185A), a tail light (185B), a transistor controlled ignition (TCI) unit (not shown), an alternator (not shown), a starter motor (not shown). Further, the vehicle 100 includes an anti-lock braking system (ABS), a synchronous braking system (SBS), or a vehicle control system (VCS)
[00029] Fig. 2 is the perspective view of the frame assembly (105). As per one embodiment of the present invention, the frame assembly (105) divided into the two parts namely; main tube top (203) and main tube bottom (204). Further, as per one embodiment of the present invention, the frame assembly (105) includes pair of rear tubes (205A, 205B) extends inclinedly rearward from a rear portion of the main tube (105B) defining a step through portion. As per one embodiment of present invention, the cross member termed as rear bridge structure (202) connects the pair of rear tubes (205A, 205B). Further, as per one embodiment of the present invention, main tube (105B) is mounted to the head tube (105A) of the vehicle and extends downwardly where the floorboard tube (206A, 206B) is welded to the main tube (105B) of the vehicle. Further, as per one aspect of the present invention, the cross tube floorboard (201) is mounted in between the pair of floorboard tube (206A, 206B) to provide the strength to the mounting of floorboard tube (206A, 206B).

[00030] Further, the main tube top (203) is mounted on a head tube (105A) with the gusset main tube top (207), ensures strength to the mounting of main tube top (203). Further, as per one embodiment of the present invention, the main tube bottom (204) is mounted with respect to the main tube top (203) with the gusset main tube bottom (208), ensures the strength to the mounting of the main tube bottom (204).
[00031] Fig. 3 is the enlarged view of the frame assembly (105). Further, as per one embodiment of the present invention, the main tube bottom (204) is mounted with the main tube top (203) at a predetermined angle A. Further, as per one embodiment of the present invention, the predetermined angle is 90 degrees with respect to the vertical axis, ensures the distribution of the force and stress on the frame assembly and also, provides enough space for the mounting of floorboard. Further, as per one aspect of the present invention, the main tube (203) top and main tube bottom (204) is further supported by the gusset main tube bottom (208) where the main tube (203) top have a straight profile with respect to gusset main tube bottom at a predetermined distance of B. Further, as per one embodiment, the distance B lies in the range of 100-105mm, ensures the strength and durability of the welded joint at 90 degrees. Further, as per one embodiment of the present invention, the pair of floorboard (206A, 206B) is mounted on the main tube (105B) through the mounting holes present in the gusset main tube bottom (204).

(00032] Fig. 4 is the exploded view of the frame assembly (105). As per one embodiment of the present invention, the pair of floorboard (206A, 206B) is mounted to the main tube (105B) through the mounting holes (401A, 401B) in the gusset main tube bottom (208) (as shown in fig. 4a), ensures the strength of the floorboard tube (206A, 206B).
[00033] The embodiments explained in Fig. 3. Fig. 4 of the present invention helps in minimizing the use of new components,
[00034] Advantageously, the embodiments of the present invention, describes the potential modifications in the mounting of main tube top and main tube bottom of the step through vehicle. This facilitates the simple and easy mounting of the main tube top and main tube bottom which ensures the ease of manufacturing.
[00035] Many other improvements and modifications may be incorporated herein without deviating from the scope of the invention.
We Claim
1. A step through type vehicle (100), said vehicle (100) comprising:
a frame assembly (105) for skeletal support to said vehicle (100); said frame assembly includes head tube (105A), main tube (105B), floorboard tubes (206A, 206B) and rear tubes (205A, 205B);
said main tube (105B) includes main tube top (203) and main tube bottom (204);
said main tube bottom (204) is mounted to said main tube top (203) with the gusset main tube bottom (208).
2. The step through vehicle (100) as claimed in claim I, wherein said main tube bottom (204) is mounted at a predetermined angle A.
3. The step through vehicle (100) as claimed in claim 1, wherein said predetermined angle A is 90 degree with respect to vertical axis.
4. The step through type vehicle (100) as claimed in claim 1, wherein said main tube top (203) is mounted to the head tube (105A) with the gusset main tube top (207).
5. The step through type vehicle (100) as claimed in claim 1, wherein said pair of floorboard tube (206A, 206B) is mounted to gusset main tube bottom (204).
6. The step through vehicle (100) as claimed in claim 1, said gusset main tube includes at least a mounting hole (401 A, 401B).

7. The step through vehicle (100) as claimed in claim I, said main tube top (203) is having a straight profile at a predetermined distance B with respect to gusset main tube bottom (208).
8. The step through vehicle (100) as claimed in claim 7, said predetermined distance B is in the range of 100-105mm.