Claims:We Claim:

1. A mechanism for steering column angular position adjustment in agricultural tractors, the steering column comprising:
an upper column tube assembly and a lower column tube assembly connected by a joint, the upper column tube assembly having ,
• a movable bracket welded with a tube;
• a fixed bracket mounted on left hand side of a vehicle main mounting bracket;
• a freely rotating bracket mounted on right hand side of the vehicle main mounting bracket for ease of alignment and fitment, and
• a stopper for controlling angular movement of the upper column tube assembly with respect to the lower column tube assembly; and
a ratchet and pawl mechanism having,
• a ratchet with straight tooth design, increased thickness and depth, the ratchet connected to the fixed bracket of the upper column tube assembly;
• a pawl with straight tooth design, increased thickness and depth, the pawl pivoted and guided on the fixed bracket of the upper column tube assembly;
• a return spring connected to the pawl;
• a stopper bracket for the pawl;
• a spring for controlling the pawl stopper bracket;
• a foot operated pedal rod connected to the stopper bracket for the pawl,
• a stopper plate for the pawl, ,
• a link plate assembled with the pawl; and
• a spring to hold the stopper,
wherein upon operating the foot pedal by the driver, the stopper bracket of the pawl moves down, and the link plate pulls the pawl down thereby disengaging the pawl from the ratchet and unlocking the upper column tube assembly from the lower column tube assembly for tilting by the driver, and when the foot pedal is released, the pawl return spring pulls the pawl back to make the pawl engage with ratchet to lock the steering column.

2. The mechanism for steering column angular position adjustment as claimed in claim 1, wherein the pawl stopper bracket is fixed on an anchor bracket which provides support when the pawl stopper bracket moves down.

3. The mechanism for steering column angular position adjustment as claimed in claim 1, wherein the link plate is fixed on the pawl stopper bracket with the support of pin on one end and a bush which hold the pawl on the other end.

4. The mechanism for steering column angular position adjustment as claimed in claim 1, wherein the link plate assembled with the pawl by a spacer.

, Description:Field of invention

The present invention relates to a mechanism for steering column angular position adjustment in agricultural tractors and more particularly, the present invention relates to the steering column assembly designed in single piece with inbuilt linkages for tilting action.

Background of the invention

The steering column is a device intended primarily for connecting a steering wheel to a hydrostatic steering unit in tractors. The steering column transfers the driver's input torque from the steering wheel to the hydrostatic steering unit which turns front road wheels through use of power steering cylinders and other components.

Apart from the primary basic function stated above, when the steering column performs secondary basic function by providing angular adjustment of steering wheel for better driving comfort, it is called as tiltable type steering column.

The steering column also performs other secondary functions like a structure for mounting of FR Switch, combination switch, scuttle cover and many other parts.
In automobile industry, the steering columns are locked and unlocked in its position with the help of a friction mechanism, a cam operated adjusting mechanism, a gas spring mechanism, a ratchet and pawl mechanism, and the like.

In agricultural tractors, the gas spring mechanism, and ratchet and pawl mechanism are widely used for adjusting the angular position of steering wheel. Specifically, tiltable type steering columns can be either operated with hand or foot.

The gas spring tilting mechanism for adjusting the angular position of steering wheel has got its own limitation because of the gas spring failure when excess force is applied by the driver on the foot pedal while trying to unlock the steering column. Hence, most of the gas springs tilting mechanisms are made hand operated. Further, in the gas spring tilting mechanism, the steering column can be tilted by 2 positions only i.e. towards the driver and away from the driver.

Another mechanism of adjusting the angular position of steering wheel is using ratchet and pawl mechanism. The tilt steering column is an arrangement of upper and lower column assembly which uses the ratchet and pawl to lock/unlock the position of steering column at multiple positions towards/away from the driver as per ergonomic requirement. However, in this mechanism, linkages and steering column are not integrated. Hence, it becomes more complicated and requires more number of child linkage parts for actuating the column. Further, the existing design of the tilt steering column with ratchet and pawl mechanism cannot be standardized across different vehicle platforms.

Accordingly, there exists a need to provide a tiltable type steering column with inbuilt mechanical linkages which can be flexibly integrated and standardized across different vehicle platforms, and which overcomes abovementioned drawbacks.

Objects of the present invention

An object of the present invention is to provide a modular single piece steering column assembly with inbuilt linkages for tilting action.

Another object of the present invention is to reduce tilt steering column assembly cycle time on tractor.

Yet another object of the present invention is to provide fail safe linkage mechanism for the tilt steering column assembly that enhances customer satisfaction.

Summary of the invention

Accordingly, the present invention provides a mechanism for steering column angular position adjustment in agricultural tractors. The steering column comprises an upper column tube assembly and a lower column tube assembly connected by a joint. The upper column tube assembly comprises a movable bracket welded with a tube, a fixed bracket mounted on left hand side of a vehicle main mounting bracket, a freely rotating bracket mounted on right hand side of the vehicle main mounting bracket for ease of alignment and fitment, and a stopper for controlling angular movement of the upper column tube assembly with respect to the lower column tube assembly.

The steering column further comprises a ratchet and pawl mechanism. The ratchet and pawl mechanism comprises a ratchet with straight tooth design and increased thickness and depth. The ratchet is connected to the fixed bracket of the upper column tube assembly. The ratchet and pawl mechanism further comprises a pawl with straight tooth design, and increased thickness and depth. The pawl is pivoted and guided on the fixed bracket of the upper column tube assembly. The ratchet and pawl mechanism furthermore comprises a return spring connected to the pawl, a stopper bracket for the pawl, a spring for controlling the pawl stopper bracket movement, a foot operated pedal rod connected to the stopper bracket for the pawl, a stopper plate for the pawl, a link plate assembled with the bush which passes through Fixed bracket and Pawl.

Wherein upon operating the foot pedal by the driver, the stopper bracket of the pawl moves down, and the link plate pulls the pawl down thereby disengaging the pawl from the ratchet and unlocking the upper column tube assembly from the lower column tube assembly for tilting by the driver. Further, when the foot pedal is released, the pawl return spring pulls the pawl back to make the pawl engage with ratchet to lock the steering column.

Brief description of the figures

The objectives and features of the present invention will be more clearly understood from the following description of the invention taken in conjunction with the accompanying drawings, wherein,

Figure 1 shows a tiltable steering column with inbuilt mechanical linkages, in accordance with the present invention;

Figure 2 shows an upper column assembly of the tiltable steering column of figure 1;

Figure 3 shows a ratchet and pawl mechanism of the tiltable steering column of figure 1;

Figure 4 shows a linkage mechanism of the tiltable steering column of figure 1;

Figure 5 a and 5 b shows mechanism of tilting the tiltable steering column of figure 1; and

Figure 6 shows various tilt positions in which ratchet and pawl of the figure 3 gets engaged.

Detailed description of the present invention:

The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiment.

The present invention provides a modular single piece steering column assembly with inbuilt linkages for tilting action. The mechanism of the present invention reduce tilt steering column assembly cycle time on tractor due to inbuilt linkages within the steering column. Further, the mechanism of the present invention provides Fail-Safe linkage mechanism for the tilt steering column assembly that enhances customer satisfaction.

For the better understanding of this invention, reference would now be made to the embodiment illustrated in greater depth in the accompanying figures and description herein below, further, in the following figures, the same reference numerals are used to identify the same components in various views/figures.

Referring now to figure 1- 6, there is shown a mechanism for steering column (100) angular position adjustment in agricultural tractors, in accordance with the present invention. As shown in figure 1, the steering column (100) comprises an upper column tube assembly (10), and a lower column tube assembly (32). The upper column tube assembly (10) and the lower column tube assembly (32) are connected by a universal joint (30). In an embodiment, the upper column tube assembly (10) is made of ERW (Electric Resistance Welded) tube in which steering shaft is assembled along with ball bearing at the top and bottom. These ball bearings reduce rotational friction and support radial and axial loads. The steering column (100) further comprises a ratchet and pawl mechanism (40).

The upper column tube assembly (10) of the steering column (100) is shown in figure 2. The upper column tube assembly (10) comprises a movable bracket (12) welded with a tube, a fixed bracket (14) mounted on left hand side of a vehicle main mounting bracket (not shown), and a freely rotating bracket (16) mounted on right hand side of the vehicle main mounting bracket (not shown). The freely rotating bracket (16) provides for ease of alignment and fitment. The upper column tube assembly (10) further comprises a stopper (18) for controlling angular movement of the upper column tube assembly (10) with respect to the lower column tube assembly (32). In an embodiment, the stopper (18) is welded on the fixed bracket (14)

In an embodiment, the fixed bracket (14) includes mounting bosses (14a) welded thereto.

In another embodiment, the movable bracket (12), the fixed bracket (14) and the freely rotating bracket (16) are made of E350C material as the movable bracket (12), the fixed bracket (14) and the freely rotating bracket (16) need to resist deformation when load gets transferred thereon while tilting the column.

As shown in figure 3, a ratchet and pawl mechanism (40) of the steering column (100) is shown. The ratchet and pawl mechanism (40) comprises a ratchet (42). The ratchet (42) as shown in figure 6 includes straight tooth design, increased thickness and depth as compared to the prior art ratchet. The ratchet (42) is connected to the fixed bracket (14) of the upper column tube assembly (10).

The ratchet and pawl mechanism (40) further comprises a pawl (44). The pawl (44) as shown in figure 6 includes with straight tooth design, and increased thickness and depth as compared to the prior art pawl. The pawl (44) is pivoted and guided on the fixed bracket (14) of the upper column tube assembly (10).

The ratchet and pawl mechanism (40) furthermore comprises a return spring (46) connected to the pawl (44), a stopper bracket (48) for the pawl (44), a first spring (50) for controlling the pawl stopper bracket (48), a foot operated pedal rod (52) connected to the stopper bracket (48) for the pawl (44), a stopper plate (54) for the pawl (44), a link plate (56) assembled with the pawl (44) and a spring (58) to hold the stopper (18).

In an embodiment, the ratchet (42) and pawl (44) are made of En19 material. This material is selected because of its good ductility and its resistance to shock and wear properties. In another embodiment, the return spring (46) connected to the pawl (44), and the first springs (50) for controlling the pawl stopper bracket (48) are extension springs. The extension springs absorb and store energy as well as create a resistance to a pulling force. Further, the pawl stopper bracket (48) is made of E350C material.

Referring now to figure 4, a linkage mechanism of the steering column (100) is shown. The linkage mechanism is designed to lock/unlock the steering column at different angular positions. This linkage mechanism comprises a splined bush (42a) which holds the ratchet (42), a bush (44a) which holds the pawl (44), a pin (56a) for supporting the link plate (56), and an anchor bracket (50a) for the first spring (50) for controlling the pawl stopper bracket (48), an anchor bracket (52a) for the foot operated pedal rod (52) and a resting pad (60).

In an embodiment, the pawl stopper bracket (48) is fixed on an anchor bracket (48a) which provides support when the pawl stopper bracket (48) moves down.

In another embodiment, the link plate (56) is fixed on the pawl stopper bracket (48) with the support of pin (56a) on one end and a bush (44a) which hold the pawl (44) on the other end. The link plate (56) assembled with the pawl (44) by a spacer (56b).

During operation as shown in figure 5a and 5b, when the foot pedal (52) is pressed by the driver, the stopper bracket (48) of the pawl (44) moves down, and the link plate (56) pulls the pawl (44) down thereby disengaging the pawl (44) from the ratchet (42) and unlocking the upper column tube assembly (10) from the lower column tube assembly (30) for tilting by the driver.

Further when the foot pedal is released, the pawl return spring (46) pulls the pawl (44) back to make the pawl (44) engage with ratchet (42) to lock the steering column (100).

Figure 6 shows various tilt positions such as straight ahead (A), towards (B) and away (C) from the driver position which can be achieved in the mechanism of the present invention. These positions are at an angular gap of 6.78 deg (tilt angle range 13.56 deg (+/- 6.78 deg from SAP for OS)) which is finalized based on the ergonomic requirement of the driver. This degree is achieved by designing the tooth both in ratchet (42) and pawl (44) as well as providing stopper (18) inbuilt in column for controlling the angular movement.

Thus in the present invention, both the ratchet and pawl mechanism (40) and linkage mechanism are all in built in the steering column (100) which is unique and can be integrated flexibly across different vehicle platforms.

Advantages of the invention

1. The mechanism of the present invention provides a modular design for easy installation and flexible integration across different vehicle platforms.
2. The mechanism of the present invention includes lesser number of child parts when compared with prior art mechanism.
3. Using the mechanism of the present invention, a tilt steering column assembly cycle time on tractor is reduced considerably.
4. The mechanism of the present invention provides a failsafe linkage mechanism that enhances customer satisfaction when compared with existing gas spring tilting mechanism.

The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention described in the present embodiment. Detailed descriptions of the preferred embodiment are provided herein; however, it is to be understood that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure, or matter. The embodiments of the invention as described above and the methods disclosed herein will suggest further modification and alterations to those skilled in the art. Such further modifications and alterations may be made without departing from the spirit and scope of the invention.