Title of Invention

A COMBINED TRACTION-STEERING MECHANISM FOR A VEHICLE

Abstract A combined traction-steering mechanism for a vehicle comprising a front wheel and a rear wheel for steering and propelling the vehicle, said wheels being driven by manual effort or a prime mover through a drive system; two idler wheels free to spin on their axes, the arrangement being such that the steering action rotates the axes of the front and rear wheels to the same extent, but in opposite directions so as to keep the intersecting point of the axes on the bisector of the line joining the centres of the said front and rear wheels; the axes of the idler wheels coincide with the bisector of the line joining the centres of the front and rear wheels; all four wheels roll along circles whose centres coincide at some point on the bisector of the line joining the centres of the front and rear wheels; and the centre of rotation of the vehicle is always equidistant from the front and rear wheels.
Full Text

This invention relates to a combined traction-steering mechanism for a vehicle. Particularly this invention relates to a mechanism employed for a wheeled vehicle requiring extreme mobility for operating in a crowded floor. The vehicle has to turn around on a spot by swiveling about an axis through the center of the vehicle without moving in any direction when necessary. A battle tank has such extreme maneuverability, but it is not a wheeled vehicle and tracked vehicles are not suitable for paved surfaces. A wheel chair propelled by the occupant of the vehicle by turning the wheels on either side by hand is another example of a vehicle, which can swivel around on a spot, and in this case it is suitable for operation on a paved surface. The mechanism proposed herein is however different from that of the known wheel chair.
A combined traction-steering mechanism for a vehicle, according to this invention, comprise a front wheel and a rear wheel for steering and propelling the vehicle the said wheels being driven by manual effort or a prime mover though a dive system; two idler wheels free to spin on their axes of the front and rear wheels to the same extent, but in opposite directions so as to keep the centers of the said front and rear wheels; the axes of the idler wheels coincide with the bisector of the line joining the centers of the front and rear wheels; all four wheels roll along circles whose centers coincide at some point on the bisector of the line joining the centers of the front and rear wheels; and the center of rotation of the vehicle is always equidistant from the front and rear wheels.
This invention will now be described with reference to the accompanying drawings which illustrate, by way of example and not by way of limitation, a preferred embodiment of the combined traction-steering mechanism for a vehicle' proposed herein Fig. I illustrates the principle of operation of the vehicle. And Figures 2A, 2B and 2C

illustrate the drive mechanism comprising a gearing system of spur, bevel and differential gears.
^ Figure 1 illustrates the principle of a wheeled vehicle, which uses art alternative strategy to achieve the degree of maneuverability possible for a wheel chair. In this vehicle a wheel at the front end and another at the rear end is driven by the tractive agency (e.g. human agency, motor or engine ) and the same wheels are also used to steer the vehicle. The steering action rotates the wheel axes to the same extent, but in opposite directions so as to keep the inteissgting point of the axes on the bisector of the line joining centers of the two wheels. The other two wheels are free to spin on their axes but are not driven. The axes of these free wheels are fixed coinciding with the bisector of the line joining the centers of the active wheels. As a result of these conditions all four wheels roll along circles whose centers co-inside at some point on the bisector of the line joining the centers of the two active driven wheels. This point can be even at the mid point between the two active wheels. Further as the center of rotation of the vehicle is always equidistant from the two active wheels, these wheels have to spin on their axes at the same speed.
The requirements for traction and steering explained above can be summarized as follows:
1. The steering input should cause the two active wheels to swivel about their respective steering king pins to the same extent, but in opposite sense such that the intersection of their axes is always equidistant from the two wheel centers.
2. The traction input should cause the two active wheels to spin on their axes to the same extent in the same sense.

3. The steering action should not cause traction to any extent and the traction should not cause any disturbance to the steering action.
The drive mechanism for satisfying the three requirements given above is shown diagrammatically on figures 2A, 2B & 2C. Elements
indicated by Bl, B2, B17 are bevel gears. Elements indicated by Gl,
G2, ....G12 are spur gears. Elements indicated by SI, S2, S3, SI 7 are
shafts or axles. Elements Dl & D2 are differential gear mechanisms whose internal details need not concern us here as these are well known in the art. Wl & W2 are the two wheels which are driven and steered by the mechanism. In the position of the wheels illustrated in the figures the vehicle will swivel around about a point mid way between the wheels when traction input is applied. Of course the axes of these wheels may be oriented in any direction in general so as to satisfy requirement (1).
The vehicle is driven by traction input applied to shaft S5 and steered by rotating shaft SI in either sense. Figure 2B illustrates the rotations of the various elements when traction input is applied to the mechanism. Figure 2C illustrates the rotations of the various elements when the steering input is applied.
A detailed description of the relevant features of the gear mechanism illustrated by figures 2A, 2B, and 2C is given in this paragraph in the interest of clarity though these diagrams are self explanatory:- Gear B5 is fixed to shaft SI and engages gear B4. Gear Bl is fixed to shaft S5 and engages with B2 and B3 as shown. Gear B2 is fixed to shaft S6 and gear B3 is fixed to shaft S7. Gears B4, G1, B6, G5, and BIO are fixed to shaft S2. Gear B6 engages gear B7 fixed to hollow shaft S3. Gear BIO engages geaf'Bl I fixed to hollow shaft S4. Gear Gl engages with gear G2 which is fixed to shaft S8. Gear G5 engages with

gear G6 which is fixed to shaft S9. Gear G3 is fixed to the planet carrier or cage of the differential Dl. So also gear G7 is fixed to the planet carrier of differential D2. G3 engages G4 which is fixed to shaft SIO. Q7 engages G8 which is fixed to shaft SI 1. Bevel gear B8 which is fixed to- shaft SIO engages with gear B9 which is fixed to shaft SI2. Bevel gear B12 is fixed to shaft S11 and engages B13 fixed to shaft S13. Bevel gear B14 is fixed to shaft S12 which is concentric with hollow shaft S3. So also bevel gear B16 is fixed to shaft S13 which is concentric with hollow shaft S4. Bevel gear B14 engages gear B15 which is fixed to shaft SI4. Bevel gear B16 engages B17 fixed to shaft SI5. Rotation of shaft S14 is transferred to wheel axle S16 to which the wheel Wl is fixed via gears G9 and Gil. Rotation of shaft S15 is transferred to wheel axle S17 to which the wheel W2 is fixed via gears G10 and GI2. The fork which carries shaft S14 and wheel axle S16 is fixed to the hollow shaft S3. The fork which carries shaft SI5 and wheel axle S17 is fixed to hollow shaft S4.
The angular Totation of elements will be identified by the element to which will be appended the symbol "(0)". Thus G3(0) will stand for the angle through which the gear G3 is rotated, S4(0) stands for rotation angle of shaft S4 and so on. K1, K2, K3, & K4 are constants.
The action of the differentials Dl and D2 can be expressed by the relationships.
G3(0)='/2[S6(e)+S8(G)J — (Al)
G7(9)=,/2[S7(e)+S9(e)J — (A2)
Further the gear ratios are such that the following rotations hold:-
S2(9) =K, Sl(6) (Bl)
K2 S5(9) = S6(0) = -S7(0) —-- (B2)

S3(0) = Ki S2(0) —- (CI)
S4(0) = -K3 S2(0) (C2)
S12(9) = K3 S10(6) (C3)
S13(0) - -K3 S11 (0) - (C4)
S8(0) = G2(0) = -2.G1(0) = -2.S2(0) (Dl)
S9(0) = G6(0) = -2.G5(0) = -2.S2(0) -— - (D2)
SIO(0) = G4(0) = -G3(0) (El)
SI 1(0) = G8(0)=-G7(0) -— (E2)
S16(0)=K4 [S12(O)-S3(0)] (Fl)
S17(0)- K4 [S13(0)-S4 (0)J —-- - (F2)
To understand equations (Fl) , one should note that as shaft S14 and S16 are rotating on axes fixed to hollow shaft S3 their rotation is a function of the rotation of S12 relative to shaft S3 and not relative to the frame of the vehicle chassis. The same argument holds for equation (F2) which connects rotations of S13 and S4 to that of S17.
The six sets of equations (A), (B), (C), (D), (E) & (F) are axioms which simply state the relationships between the elements of the mechanism which are apparent given its configuration. Now using these equations we can prove that the mechanism does satisfy all three requirements stated above.
From equations (Dl) and (Bl):-
S8(0) = -2.K, . SI (9) — (1)

From (AI), (B2) and (1):-
G3(9) = V2 [K2. S5(0) - 2. K, .S1 (0)J - —-- (2)
From (C3), (El) and (2):-
S42(0) = K,{- '/2 [K2 .S5(0)-2.K, .Sl(G)Jj
That is:
SI2(0) = - ,/2K2K3.S5(e) + K, K3.S1(0) — - (3)
From (CI), &(B1)>
S3(6) = K, K3 .Sl(9) -- (4)
From(Fl), (3)&(4)
S16(0) = - VJ K2 K3 K4 .S5(0) (5)
Equation (5) shows that the rotation of the wheel axle SI6 is proportional to the traction input rotation given to S5 and is independent of the steering input applied to shaft SI.Now a similar argument can prove that rotation of traction input S5(G) will produce the same rotation -1/2 K2, K3, K4 .S5ia) on wheel axle S17 also.
From (D2) and (Bl)
S9(9) = -2.K, .SI (9) (6)
From(A2),(B2),&(6)
G7(O)=,/2-[K2.S5(0)-2.K, .Sl(G)j (7)
From(C4),(E2)and(7)
SI3(0) = -K3 {-'/2[-K2. S5(0)-2.K, .S1(0)]| That is:
S13(0) = -I/2K2K3.S5(0)-K, K3.S1(0) (8)

From(C2)&(Bl)
S4(0) = -K, K, .S1(G) (9)
From (F2), (8), (9):-
S17(G) = - »/2 K2 K, K4.S5(0) —-- (10)
As for the steering; from (C1) & (BI) we have
S3(9) = K, K3. S1 (9) - - (II)
And from (C2)&(B1)
S4(9) = -K,K,.S](e) - (12) ; v i$
A I J "
Equations (5), (10), (11) and (12) have established that:- \ . i *:' 'AJOO> r
a) Traction input applied to shaft S5 produces equal reflation of) both driven wheels on their axles in the same sense andjhal.,th€^ traction input has no effect on shafts S3 Uriel S4 which determine the radius of turns in steering the vehicle.
/-brf'Steering input applied to shaft SI causes shafts S3 and S4 to
( rotate through equal angles in opposite sense and that it does J
V not cause'Siy rotation of wheel axles S16 and S17.
A word of explanation concerning point (a) above in relation to
, Figure 2B:-
In Figure 2B it may appear that the traction input is causing
the wheels Wl and W2 to rotate in opposite sense in violation of
) equations (5) and (10). The reason for this will become clear if one
goes back to the principle of the vehicle shown on figure 1. The
.
rotation ot the wheels relative to the forks on which they are\ mounted does conform to equations (5) and (10). However as
shown in the figures the forks have to be rotated by shafts S3 and
S4 through 90° in- opposite senses from their "straight ahead"
positions, so relative to the frame of the vehicle the wheels turn in
opposite senses making the vehicle swivel sound on the spot.

The proof is complete as it stands. However to appreciate just how the torques applied to the traction input shaft S5 and steering input shaft S1 avoid interfering with each other the following explanation is provided:-
Consider figure 2C which shows the effect of steering input applied to S1 in the absence of tractive input at shaft S5. It is of course clear how the hollow shafts S3 and S4 are rotated in opposite sense. The torques transmitted to gears G2 and G6 acts on G3 and G7 respectively through differential mechanisms Dl & D2. In doing this; torques are indeed imposed on shafts S6 and S7, but these torques are in the same sense and gears B2 and B3 fixed to these shafts cannot rotate in the same sense due to their engagement with B1. So what happens is that these torques cancel each other in their effect on B1.
Now consider figure 2B which shows the effect of a traction input appliecTtb shaft S5 in the absence of any steering effort on shaft SI. In this case B2 and B3 are torqued in opposite directions by the traction input to shaft S5, when transmitting the tractive torque from S6 to G3 and S7 to G7 the differentials Dl and D2 now applies torques in opposite senses to gears G2 and G6 which in turn try to rotate Gl & G5 in opposite directions. This is of course impossible as Gl & G5 are fixed to the same shaft S2 and so again the effect on S2 of torques on G1 and G5 cancels out and is not transmitted to SI. Thus steering input torque does not create any net torque on traction input and vice versa.


We Claim:
1. .A combined traction-steering mechanism for a vehicle
comprising a front wheel and a rear wheel for steering and propelling the vehicle, said wheels being driven by manual effort or a prime mover through a drive system; two idler wheels free to spin on their axes, the arrangement being such that the steering action rotates the axes of the front and rear wheels to the same extent, but in opposite directions so as to keep the intersecting point of the axes on the bisector of the line joining the centres of the said front and rear wheels; the axes of the idler wheels coincide with the bisector of the line joining the centres of the front and rear wheels; all four wheels roll along circles whose centres coincide at some point on the bisector of the line joining the centres of the front and rear wheels; and the centre of rotation of the vehicle is always equidistant from the front and rear wheels.
2. A combined traction-steering mechanism for a vehicle
substantially as herein described with reference to, and, as
illustrated in, Figs. 1, 2A, 2B, 2C of the accompanying
drawings.


Documents:

0103-che-2003 abstract.pdf

0103-che-2003 claims duplicate.pdf

0103-che-2003 claims.pdf

0103-che-2003 correspondence others.pdf

0103-che-2003 correspondence po.pdf

0103-che-2003 description (complete) duplicate.pdf

0103-che-2003 description (complete).pdf

0103-che-2003 drawings.pdf

0103-che-2003 form-1.pdf

0103-che-2003 form-19.pdf

0103-che-2003 form-26.pdf


Patent Number 205607
Indian Patent Application Number 103/CHE/2003
PG Journal Number 26/2007
Publication Date 29-Jun-2007
Grant Date 05-Apr-2007
Date of Filing 05-Feb-2003
Name of Patentee M/S. ELECTRONICS RECEARCH AND DEVELOPMENT CENTER OF INDIA
Applicant Address VELLAYAMBALAM, THIRUVANANTHAPURAM
Inventors:
# Inventor's Name Inventor's Address
1 NE NE
PCT International Classification Number B60B19/02
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA