FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10; rule 13)
TITLE OF INVENTION
Improved Fifth Wheel Assembly Mounted On Vehicle For Attaching Trailer To The Vehicle


APPLICANTS
TATA MOTORS LIMITED, an Indian company
having its registered office at Bombay House,
24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India
INVENTORS
Mr. Mahavir Chimad, Mr. Jeevan Ghadge
And Mr. Rakesh Nikam
AH are Indian Nationals
of TATA MOTORS LIMITED,
an Indian company having its registered office
at Bombay House, 24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India

PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner
in which it is to be performed.


FIELD OF INVENTION
This invention relates to an improved fifth wheel assembly mounted on vehicle for attaching trailer to the vehicle.
BACKGROUND OF INVENTION
A Fifth wheel assembly mounted on vehicle is shown in Fig-1. Fifth Wheel coupling (la) has standard mounting dimensions all over the world. But vehicle frames (1) are built as per manufacturer's part commonality and functional requirements. Substructure (3) is the interface between vehicle and fifth wheel. Fifth wheel substructure should transfer concentrated load of trailer evenly to larger area of frame. Fifth wheel should transmit vertical downward load of trailer(2) to chassis. Due to road irregularities, twisting and pitching loads are also transmitted from ground to trailer. . Substructure weight should be as low as possible to give better payload capacity without compromising on strength and rigidity to give long chassis life. But the existing systems are very bulky, and expensive. Also the fifth wheel height affects the dynamic stability of vehicle and is to be kept as low as possible for better stability of the vehicle. Each vehicle manufacturer may have peculiar requirements of chassis dimensions, giving rise to multitude of structures seen in use and with above mentioned drawbacks.
PRIOR ART
A common type of prior art is shown in Fig-2. It has a Z-pIate (1,1a) placed on frame top surface, with side support plates (4,4a,5,5a,6,6a) to fasten to frame web. Welded assembly of corrugated plate and longitudinal closed-C channels (3) is placed on the Z-plate and bolted to it. The closed-C rests on the Z-plate lower flange while corrugated plate rests on upper flange. Fifth wheel coupling (not shown) is bolted to top of corrugated plate. Hat section cross-members (2) connect the z-plates at locations towards front of coupling. The characteristics of the design are as follows.
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Height of fifth wheel from frame top is large and height of Center of Gravity increases and so the possibility of overturning due to instability. This is due to constraint on bolt hole location w.r.t. bend radius of Z-plate . Consequently the weight of structure increases. Also, load is transferred to frame long-members on both web and flange. Shear centre of a C-section frame is on the outer side of C. The resulting load from prior art is imposed on a plane between flange and web as shown. So the C-section of frame is not optimally used. To counteract the increased deformations, the side support plates and Z-plate have to be made longer to distribute load to larger area of frame. To reduce some weight, three separate support plates on each side are used.
Another type of prior art is shown in Fig-3. It has a Z-plate (3,3a) with hat cross-members (2) arrangement. Z-plate (3,3a) is resting on frame top surface and bolted to frame by side reinforcement plates (4,4a,5,5a). Sub-assembly of coupling mounting plates (1) and hat cross-members (2) is welded together. This sub¬assembly is bolted to fifth wheel coupling (not shown). Resulting sub-assembly is placed on the Z-plate and bolted to it. Hat-section (2) rests on Z-plate lower flange. The characteristics of the second prior art are as follows. Cross-reinforcement just below the coupling makes this structure more rigid than earlier prior art. Strength in twisting is improved. But the hat-section cross-members require press tools and resulting higher initial costs. Also the assembly involves 7 steps on assembly line and makes the assembly cumbersome and increases the cost.
OBJECTS OF INVENTION
The main object of this invention is to obviate the aforementioned drawbacks by providing an improved fifth wheel assembly mounted on vehicle for attaching trailer to the vehicle, which will have less weight and height with simpler assembly.
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SUMMARY OF INVENTION
An improved fifth wheel assembly mounted on vehicle for attaching trailer to the vehicle comprising:
a sub-assembly of fifth wheel coupling (3), corrugated plate (4) and substructure (2) which is dropped on bracket coupler (1,1a) and bolted to it wherein said bracket couplers (1,1a) are simple L-plates to transfer the load coming from said fifth wheel to frame web only so that load path is closer to C-frame shear center.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 shows assembly of the "a fifth wheel assembly mounted on vehicle for
attaching trailer to the vehicle".
Figure 2 shows assembly of the Prior Art 1.
Figure 3 shows assembly of the Prior Art 2.
Figure 4 shows assembly of the "a fifth wheel assembly mounted on vehicle for
attaching trailer to the vehicle" according to the instant invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only, and not for the purpose of limiting the same, the instant invention shown in Fig-4 herein consists of bracket coupler (1,1a) bolted to frame web. A sub-assembly of fifth wheel coupling (3), corrugated plate (4) and substructure (2) is made. This is dropped on bracket coupler (1,1a) and bolted to it.
Bracket couplers (1,1a) are simple L-plates made without specialized tooling. They transfer the load coming from fifth wheel to the frame web only, so that load path is closer to C-frame shear center. This ensures optimal utilisation of frame material. Bracket couplers are fastened together by assembly substructure (2) which provides
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torsional rigidity to the structure. Assembly substructure (2) consists of two smaller L-plates (2a,2a') connected by welded closed-C channels (2b). The connecting C-charmels have a small clearance with frame top surface. So load transfer is only at the frame sides (web) and not at top flange. Closed-C channels are used for higher torsional rigidity compared to the open hat-sections used in prior art.
Smaller ribs (2c) are strategically added to assembly substructure to ensure torsional rigidity. The cross C-channels are strategically located to overlap with base of corrugated plate. (Fig 4-View A). The number and location is optimized based on best practices. Truck operators may want to move the fifth wheel coupling forward along frame in case of short-overhang trailers. So provision is made for multiple sets of mounting holes on the bracket couplers (1,1a). The cross c-channels are located such that in both positions they overlap with base of corrugated plate. The connecting cross-channels (2b) and the corrugated plate (4) have such sections that, no specialized tooling is required.
The connecting c-channels have a small clearance with frame top surface. So load transfer is only at the frame sides (web) and not at top flange. The overall arrangement results in lower fifth wheel top-plate height. This improves the dynamic stability of vehicle-enhancing safety of operation. The compact assembly produces weight savings of around 30% in this structure over prior art. The resting area for corrugated plate (4) on frame is reduced to level sufficient for the application. Final assembly line work involves only 3 steps. So operations on assembly line are avoided. Consequently inventory and management overheads are avoided. Thus overall there is large saving in initial cost of product and light-weight structure gives better payload capacity to the truck operator.
There are many advantages of the instant inventions as described below:
1. A fifth wheel coupling sub-structure that involves use of L-plate instead of traditional Z-plate. This decreases the space to be set aside for sheet metal
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parts' bend radius, so that overall structure height is lesser. This improves dynamic stability of vehicle.
2. Further, an assembly that transfers load from trailer to frame nearer to shear-center—thus optimizing structure weight and providing sufficient structural strength.
3. Further, an assembly where cross-coupling members (closed C-channels) and corrugations of corrugated plate are matched to ensure most efficient load transfer path from fifth wheel pedestal to frame.
4. Further, a principle of designing sub-structure based on points 1 to 3, which will result in a structure with minimum weight, cost and complexity.
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.
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WE CLAIM
1. An improved fifth wheel assembly mounted on vehicle for attaching trailer to
the vehicle comprising:
a sub-assembly comprising a fifth wheel coupling, a corrugated plate and a sub-structure;
bracket couplers configured to mount said sub-assembly;
cross-coupling members located to overlap with base of said corrugated plate; wherein said bracket couplers are 'L' plates provided to transfer load coming from said fifth wheel coupling to vehicle frame web so that load path is closer to said shear center of said cross-coupling members.
2. The improved fifth wheel assembly as claimed in Claim 1, wherein said bracket couplers are fastened together by said substructure which provides torsional rigidity to said assembly.
3. The improved fifth wheel assembly as claimed in Claim 1, wherein said substructure consists of two smaller 'L'plates connected by said cross coupling members such that the cross coupling members have a small clearance with top surface of said vehicle frame.
4. The improved fifth wheel assembly as claimed in Claim 1 and 3, wherein
said cross coupling members are closed 'C section channels
5. The improved fifth wheel assembly as claimed in Claim 1, wherein small ribs are provided on said substructure to ensure torsional rigidity.
6. The improved fifth wheel assembly as claimed in Claim 1, wherein said bracket couplers comprises multiple sets of mounting holes to provide versatility for
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various mounting positions of said fifth wheel coupling along vehicle frame for various kinds of trailers.
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7. The improved fifth wheel assembly mounted on vehicle for attaching trailer to the vehicle as claimed in Claim 6, wherein the closed 'C section channels are located such that in any mounting position they overlap with base of said corrugated plate..
8. The improved fifth wheel assembly as claimed in Claim 4, wherein said connecting cross C- section channels and the corrugated plate (4) have such sections that no specialized tooling is required for assembly.
9. The improved fifth wheel assembly as claimed in Claim 1, wherein said cross-coupling members and corrugations of said corrugated plate are matched to ensure most efficient load transfer path from fifth wheel coupling to frame
10. An improved fifth wheel assembly mounted on vehicle for attaching trailer to the vehicle as herein described and illustrated in figures of the accompanying drawings.