Title of Invention

A TWIN LEVER WORM AND ROLLER MANUAL STEERING GEAR FOR A TRACTOR

Abstract A twin lever worm and roller manual steering gear for a tractor comprisin: a steering column provided with a worm; a toothed roner meshin: with the 'Worm; the said roner moving on a circular arc along the worm, whenever the steering column and thus the worm rotates, said toothed roner beinc howed in an opening of the primary rocker shaft and attached to the said openinc such that it has freedom to roll Creely; rlrst secmental cear teeth provided on the primary rotker shaft opposite the said opening second segmental gear teeth provide on the secondary rocker shaft and meshing with the first segmental gear teeth, said worm being spaced from the said roller to provide a clearance sufficient to avoid the roller and worm "stickinc".
Full Text


This invention relates to a TWIN LEVER WORM AND ROLLER STEERING GEAR for a tractor
In India, tractors are mostly fitted with manual
steering gears of the single lever type or the twin
lever type, -
Both the known single lever type and the twin lever type of steering gears have their drawbacks.
The known single lever type is provided with a ball screw and nut (with recirculating balls) , or worm and toothed roller arrangement. In such single lever types, during operation of the tractor in the field, "FREE PLAY" develops due to wear between ;
Ball screw nut and rocker shaft
Worm and toothed roller An adjuster screw is provided to take up the play; however, this screw will have to be adjusted, by the operator, from time to time, manually, to reduce the play to a tolerable level.
The known twin lever type is provided with ball screw and nut (with recirculating balls) , The nut has rack teeth which meshes with a first gear. The first gear has conical teeth all round the circumference. The first gear . meshes 'with a second conical gear which has gear teeth over a segment of circumference. In this case also, adjuster screws are provided to take up the play; however, these screws will have to be adjusted, by the operator, from time to time, manually, to reduce the play to a tolerable level.

The steering gear free play is a major irritant during tractor operation in the Held. Driving the tractor, therefore, is never comfortable with this drawback associated with both the known single and twin lever types.
This invention seeks to overcome the free play drawback referred to above. Additionally, this invention provides a more effective drive arrangement as will be clear from the following further description.
The twin lever worm and roller manual steering gear for a tractor, according to this invention, comprises a steering column provided with a worm; a toothed roller meshing with the worm, the said roller moving on a circular arc along the worm, whenever the steering column, and thus the worm, rotates, said toothed roller being housed in an opening of the primary rocker shaft and attached to the said opening such that it has freedom to roll freely; first segmental gear teeth provided on the primary rocker shaft opposite the said opening; second segmental gear teeth provided on the secondary rocker shaft and meshing with the first segmental gear teeth, said worm being spaced from the said roller to provide a clearance sufficient to avoid the roller and worm ""sticking'.

The worm and toothed roller are so spaced to provide sufficient clearance to prevent sticking as the toothed roller traverses along the arc of the worm. The self-acting free play mechanism between the toothed roller housed in the Primary Rocker shaft is achieved by continuously urging the said toothed roller against the worm by means of spring loading device in the Primary rocker shaft. The second self-acting free play adjustment is achieved by continuously urging the second conical gear against the first conical gear tooth by means of spring loading device in the secondary rocker shaft.
This invention will now be described with reference to the accompanying drawings which illustrate in
Fig. 1(a). and Fig. 1(b) the known single lever steering gear with ball screw and nut with recirculating balls
Fig.2(a) and Fig.2 (b) the known single lever steering gear with worm and toothed roller.
Fig.3(a) and Fig.3(b) the known twin lever steering gear with ball screw and nut with recirculating balls.
Fig. 4 (a) and Fig. 4 (b) , by way of example, one of possible embodiments of the TWIN LEVER WORM & ROLLER STEERING GEAR according lo this invention.
referring to Figs.l (a) and 1 (b) , one of the known single lever types of steering gear is provided with a worm W and a main nut N coupled to the worm W through recirculating balls B.

As the steering column C is rotated, the nut N travels "linearly along the worm W to cause a stub S to actuate a fork F of the rocker shaft and thence a drop arm A to turn the wheels of the tractor.
Referring to Figs.2(a) and 2(b); another version of the known single lever type steering gear is provided with worm W and toothed roller R engaging with the worm W. As the steering column C is rotated the toothed roller R engaging with worm W traverses in a circular arc along the worm driving the rocker shaft T and thence the drop arm A.
In such single lever types, during operation of the tractor in the field, free play develops in the steering' mechanism. An adjuster screw H is provided to take up the play; however, this screw will have to be adjusted, by the operator, from time to time, manually, to reduce the play to a tolerable level -
Referring to Fig.3(a) and Fig.3(b),the known twin lever with a worm W and nut N- is coupled to the worm W through recirculating balls B. As the steering column C is rotated the nut N traverse linearly along the worm W and rack teeth J provided on the nut N, meshes with the conical teeth of the primary rocker shaft thus actuating the primary rocker shaft to rotate about its axis- The conical gear tooth Kl of primary rocker shaft meshes with the conical segmental gear tooth K2 of the secondary rocker shaft thus activating the secondary rocker shaft to roate about its axis.
In this case also, adjuster screws H are provided to take up the play; however, these screws will

have to be adjusted, by the operator, from time to time , manually , to reduce the p1ay to a tolerable level. Such an arrangement is not possible with the known barrel type spur gear design-
__, -

The arrangement pertaining to the embodiment just described is mechanically more effective than that of the manual steerins gears known to the art; and results in comfortable operation of the tractor continuously free from any play or possibility of the roller and worm 'sticking'.
The terms and expressions in this specification are of description and not of limitation since It will be appreciated that various other embodiments of the steering
gear proposed herein are possible without departing from the scope and ambit of this invention.



We Claims
l. A twin lever worm and roller manual steering gear for a tractor comprises. a steering column provided with a worm; a toothed roller meshing with the worm, the said roller moving on a circular are along the worm, whenever the steering column, and thus the worm, rotates, said' toothed roller being housed in an opening of the primary

rocker shaft and attached to the to the said opening such that it has freedom to roll freely; first segmental gear teeth provided on the primary rocker shaft opposite the- said opening; second segmental gear teeth provided on the secondary rocker shaft and meshing with the first segmental gear teeth, whereby whenever the steering column is rotated, the toothed roller moves along a circular arc on the worm and rotates the primary rocker shaft about its axis thus causing the first segmental gear teeth to rotate the second segmental gear teeth and thence


preceding Claims wherein the segmental gear teeth are conical.
5. A steering gear as claimed in any one of the preceding Claims where in the said first self — acting means comprise a first spring—loaded stud for continuously urging said roller against the worm -
6- A twin lever manual steering gear as claimed in any one of the preceding Claims where in the second self—acting means comprise a second spring—loaded stud for continuously urging the second gear teeth against the first gear teeth -
7. A twin layer worm and ro11er manua1 steering gear substantially as herein described with reference to, and as illustrated in, the accompanying drawings -
Dated this the 14th day of January 1999



We Claims
l. A twin lever worm and roller manual steering gear for a tractor comprises. a steering column provided with a worm; a toothed roller meshing with the worm, the said roller moving on a circular are along the worm, whenever the steering column, and thus the worm, rotates, said' toothed roller being housed in an opening of the primary

rocker shaft and attached to the to the said opening such that it has freedom to roll freely; first segmental gear teeth provided on the primary rocker shaft opposite the- said opening; second segmental gear teeth provided on the secondary rocker shaft and meshing with the first segmental gear teeth, whereby whenever the steering column is rotated, the toothed roller moves along a circular arc on the worm and rotates the primary rocker shaft about its axis thus causing the first segmental gear teeth to rotate the second segmental gear teeth and thence


preceding Claims wherein the segmental gear teeth are conical.
5. A steering gear as claimed in any one of the preceding Claims where in the said first self — acting means comprise a first spring—loaded stud for continuously urging said roller against the worm -
6- A twin lever manual steering gear as claimed in any one of the preceding Claims where in the second self—acting means comprise a second spring—loaded stud for continuously urging the second gear teeth against the first gear teeth -
7. A twin layer worm and ro11er manua1 steering gear substantially as herein described with reference to, and as illustrated in, the accompanying drawings -
Dated this the 14th day of January 1999




Documents:

052-mas-1999-abstract.pdf

052-mas-1999-claims filed.pdf

052-mas-1999-claims granted.pdf

052-mas-1999-correspondnece-others.pdf

052-mas-1999-correspondnece-po.pdf

052-mas-1999-description(complete)filed.pdf

052-mas-1999-description(complete)granted.pdf

052-mas-1999-drawings.pdf

052-mas-1999-form 1.pdf

052-mas-1999-form 19.pdf

052-mas-1999-form 26.pdf

abs-52-mas-1999.jpg


Patent Number 211926
Indian Patent Application Number 52/MAS/1999
PG Journal Number 02/2008
Publication Date 11-Jan-2008
Grant Date 13-Nov-2007
Date of Filing 14-Jan-1999
Name of Patentee RANE (MADRAS) LIMITED
Applicant Address 61 VELACHERY ROAD, VELACHERY, CHENNAI 600 042,
Inventors:
# Inventor's Name Inventor's Address
1 MANICKAM SIVA KUMAR RANE (MADRAS) LIMITED, 61 VELACHERY ROAD, VELACHERY, CHENNAI 600 042,
2 IYYAVU PACHAIYAPPAN RANE (MADRAS) LIMITED, 61 VELACHERY ROAD, VELACHERY, CHENNAI 600 042,
PCT International Classification Number B62D 3/04
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA