Claims:We claim:

1. A mechanism for steering column angular position adjustment in agricultural tractors, the steering column (100) comprising:
an upper column tube assembly (10) and a lower column tube assembly (30) connected by a universal joint (20), wherein the steering column (100) is fixed to a vehicle mounting bracket by fixed brackets (14), each located on both sides of the steering column (100);
a double sided ratchet and pawl mechanism (40) having,
• a ratchet (42) connected on both sides to the fixed brackets (14) of the upper column tube assembly (10),
• a pawl (44) pivoted and guided on the both fixed brackets (14) of the upper column tube assembly (10), wherein the pawl (44) has teeth on both sides matching with that of the ratchet (42),
• a plate spring retainer (46),
• pawl support compression springs (48) located on the plate spring retainer (46) on both sides of a pawl actuating link mechanism, and
• an adjuster cum stopper gusset (50) integrated with the pawl (42);
a linkage mechanism connected with double sided ratchet and pawl mechanism (40) to lock/unlock the steering column (100) at different angular positions, the linkage mechanism having,
• a foot plate (52) with a pedal rod (54),
• a pedal plate (56) welded with the pedal rod (54) and fixed on an anchor bracket that is welded on the lower column tube assembly (30),
• a C clamp (58) ensuring straightness of the linkage mechanism, and
• a pawl link plate (60), wherein the pedal plate (56) is connected with the pawl link plate (60) through the C clamp (58);
an adjustable stopper mechanism integrated in the linkage mechanism, the adjustable stopper mechanism having,
• a support block (62),
• an adjustment nut and bolt assembly (64), and
• a pedal spring (66) arranged for returning of the adjustable stopper mechanism to contact with the adjuster cum stopper gusset (50) when the foot plate (52) is released by a driver,
wherein, upon operating the foot plate (52) by the driver, the linkage mechanism actuates the pawl (44) to disengage from the ratchet (42) so that the C clamp (58) controls the angular motion of the pawl link plate (60) and the pedal plate (56) for unlocking the upper column tube assembly (10) from the lower column tube assembly (30) for tilting by the driver and once the foot plate (52) is released, the pawl support compression springs (48) pull the pawl (44) back for engaging with the ratchet (42), thereby locking the steering column (100) and wherein, the adjustable stopper mechanism assists the pawl (44) in reducing backlash while engagement with the ratchet (42), thereby reducing radial play and slippage of the steering column (100) at all angular positions.

2. The mechanism for steering column angular position adjustment as claimed in claim 1, wherein both the fixed brackets (14) are fixed firmly by a tube connector and half threaded bolt assembly (12).

3. The mechanism for steering column angular position adjustment as claimed in claim 1, wherein an angle forms between the pawl link plate (60) and the pedal plate (56) to prevent a reverse movement of the pedal plate (56).

4. The mechanism for steering column angular position adjustment as claimed in claim 1, wherein the linkage mechanism is a four bar mechanism that is assembled in any one way selected from a straight condition and an off-centre towards the steering column, thereby restricting reverse force.

5. The mechanism for steering column angular position adjustment as claimed in claim 1, wherein both the ratchet (42) and the pawl (44) includes straight tooth design and increased thickness and depth.

Dated 29th day of December 2018

Madhavi Vajirakar
(Agent for Applicant)
(IN/PA-2337) , Description:Cross references to related application:

Reference is made to commonly-owned application 201741011191, therefore; the disclosure of which is hereby incorporated, entitled “Mechanism for Steering Column Angular Position Adjustment in Agricultural Tractors,” filed on 29/03/2017.

Field of invention:

The present invention relates to a mechanism for steering column angular position adjustment in agricultural tractors and particularly, to a double side ratchet and pawl mechanism for steering column angular position adjustment. More particularly, the present invention relates to a positive locking mechanism for reducing radial play and pawl slippage that occurs when higher push pull force is applied on the tilt steering column when it is in lock condition in the agricultural tractors.

Background of the invention

A 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. In automobile industry, the steering columns are locked and unlocked in its position with the help of Friction mechanism; Cam operated adjusting mechanism, Gas spring mechanism, Ratchet and Pawl mechanism, etc.

For steering column angular position adjustment, tractor manufacturers use different mechanisms such as friction mechanism, a cam operated adjusting mechanism, a gas spring mechanism, single side ratchet and pawl mechanism and the like. Among those, the gas spring mechanism and the single side ratchet and pawl mechanism are widely used for adjusting the angular position. Specifically, tiltable type steering columns can be either operated with hand or foot.

The gas spring tilting mechanism for adjusting the angular position of the 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 two positions only i.e. towards the driver and away from the driver.

Another mechanism of adjusting the angular position of the steering wheel is using the single side ratchet and pawl mechanism. The tilt steering column is an arrangement of an upper and a lower column assembly which uses the ratchet and pawl to lock/unlock the position of the steering column at multiple positions towards/away from the driver as per ergonomic requirement. However, in this mechanism, either linkages or the steering column are not integrated or it may be integrated but Steering Wheel radial play is more. Hence, it becomes more complicated and requires more number of child linkage parts for actuating the column. Also, the radial play can not be eliminated using the single side ratchet and pawl mechanism. Further, in this mechanism when higher push pull force is applied on the steering wheel by the customer, either pawl slips from the ratchet or more radial play is observed by the customer on the steering wheel. The excessive radial play makes the customer uncomfortable while driving the tractors.

Accordingly, there exists a need to provide a tiltable type steering column with an adjustable stopper mechanism along with a double side ratchet and pawl and inbuilt mechanical that can be flexibly integrated across different vehicle platforms and overcomes the abovementioned drawbacks of the prior art.

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 provide an adjustable stopper mechanism for adjusting backlash between pawl and ratchet.

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

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

Summary of the present 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, a lower column tube assembly, a double sided ratchet and pawl mechanism, a linkage mechanism and an adjustable stopper mechanism. The upper column tube assembly is connected with the lower column tube assembly by a universal joint. The steering column is fixed to a vehicle mounting bracket by fixed brackets, each located on both sides of the steering column.

The double sided ratchet and pawl mechanism includes a ratchet connected on both sides to the fixed brackets, a pawl pivoted and guided on the fixed brackets, a plate spring retainer, pawl support compression springs located on the plate spring retainer on both sides of a pawl actuating link mechanism and an adjuster cum stopper gusset integrated with the pawl. The linkage mechanism is a four bar mechanism that is connected with double sided ratchet and pawl mechanism to lock/unlock the steering column at different angular positions. The linkage mechanism includes a foot plate with a pedal rod, a pedal plate, a C clamp and a pawl link plate. The pedal plate is welded with the pedal rod and fixed on an anchor bracket that is welded on the lower column tube assembly. The pedal plate is connected with the pawl link plate through the C clamp. The C-clamp ensures straightness of the linkage mechanism. The adjustable stopper mechanism is integrated in the linkage mechanism. The adjustable stopper mechanism assists the pawl in reducing backlash while engagement with the ratchet, thereby reducing radial play and slippage of the steering column at all angular positions. The adjustable stopper mechanism includes a support block, an adjustment nut and bolt assembly, and pedal spring arranged for returning of the adjustable stopper mechanism to contact with the adjuster cum stopper gusset when the foot plate is released by a driver.

During operation of the mechanism, when the foot plate is operated by the driver, the linkage mechanism disengages the pawl from the ratchet. The C clamp controls the angular motion of the pawl link plate and the pedal plate for unlocking the upper column tube assembly the lower column tube assembly for tilting by the driver. Once the foot plate is released, the pawl support compression springs pull the pawl back for engaging with the ratchet, thereby locking the steering column.

Brief description of the drawings:

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 an isometric view of a tiltable steering column with a double sided ratchet and pawl mechanism, in accordance with the present invention;

Figure 2 shows an assembly view of the double sided ratchet and pawl mechanism of the tiltable steering column of figure 1;

Figure 3 shows detailed assembly view of a linkage and adjustable stopper mechanism of the tiltable steering column of figure 1; and

Figure 4 (a) and (b) shows mechanism of tilting the tiltable steering column of figure 1.

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 mechanism for steering column angular position adjustment in agricultural tractors. An adjustable stopper mechanism is designed to assist the pawl in reducing the backlash while engagement with ratchet which in turn reduces the radial play and slippage of the steering column at all angular positions with ease. This mechanism is robust in design as it uses double side ratchet and pawl with pawl actuating linkage mechanism located at the centre. It offers benefit of easy installation across different vehicle platforms.

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 figures 1 - 4, 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 (30). The upper column tube assembly (10) and the lower column tube assembly (30) are connected by a universal joint (20). The steering column (100) is fixed to a vehicle mounting bracket (not shown) by means of fixed brackets (14), each located on both sides of the steering column. Both the fixed brackets (14) are fixed firmly by a tube connector and half threaded bolt assembly (12). In an embodiment, the upper column tube assembly 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 further comprises a double sided ratchet and pawl mechanism (40).

As shown in figure 2, the double sided ratchet and pawl mechanism (40) (hereinafter referred as, “the mechanism (40)”) of the steering column (100) is shown. The mechanism (40) comprises a ratchet (42), a pawl (44) and a plate spring retainer (46). The ratchet (42) includes straight tooth design, increased thickness and depth as compared to the prior art ratchet. The ratchet (42) is connected on both sides to the fixed brackets (14) of the upper column tube assembly (10). The pawl (44) includes straight tooth design, and increased thickness and depth as compared to the prior art pawl. Further, the pawl (44) has teeth on both sides matching with that of the ratchet (42). The pawl (44) is pivoted and guided on the fixed bracket of the upper column tube assembly. The mechanism (40) further comprises pawl support compression springs (48). The pawl support compression springs (48) are located on the plate spring retainer (46) on both sides of a pawl actuating link mechanism. Further, the pawl has got an adjuster cum stopper gusset (50) integrated with the pawl (42). In an embodiment, both the ratchet (42) and the pawl (44) are made of En19 material. This material is selected because of its good ductility, excellent work hardening properties and its resistance to shock and wear properties. Further, the plate spring retainer (46) is made of E350C material that has got good tensile and yield strength.

Referring now to figure 3, a linkage and adjustable stopper mechanism of the steering column (100) is shown. The linkage mechanism is designed to lock/unlock the steering column (100) at different angular positions. The linkage mechanism consists of a foot plate (52), a pedal rod (54), a pedal plate (56), a C clamp (58) and a pawl link plate (60). The pedal plate (56) is welded with the pedal rod (54) and fixed on an anchor bracket that is welded on the lower column tube assembly (30). The pedal plate (56) is connected with the pawl link plate (60) through the C clamp (58) such that an angle forms between the pawl link plate (60) and the pedal plate (56) to prevent a reverse movement of the pedal plate (56). In the embodiment, the pedal rod (54) is made of En8 material and the foot plate (52) is made of E250C material. In the embodiment, the linkage mechanism is always in a straight condition or off-centre towards the steering column (100) to restrict reverse force.

The adjustable stopper mechanism is designed to assist the pawl (44) in reducing the backlash while engagement with the ratchet (42) which in turn reduces the radial play and slippage of the steering column (100) at all angular positions. The adjustable stopper mechanism consists of a support block (62), an adjustment nut and bolt assembly (64) and a pedal spring (66). The pedal spring (66) helps in returning of adjustable stopper mechanism to contact with adjuster cum stopper gusset (50) when the foot plate (52) is released by a driver.

Now, referring now to figure 4, an operation of the mechanism for steering column (100) angular position adjustment in the agricultural tractors is shown in accordance with the present invention. The figure 4 (a) shows position of the linkage mechanism when the foot plate (52) is not pressed. In this condition, the ratchet (42) and the pawl (44) are in engaged condition on both sides. The bolt and nut are adjusted to close the clearance observed between the ratchet (42) and the pawl (44). This ensures no radial play when higher push pull force is applied on the steering wheel. The C clamp (58) ensures straightness of the linkage mechanism.

The figure 4 (b) shows the linkage mechanism function when the foot plate (52) is pressed. This linkage mechanism that actuates the pawl (44) is a four bar mechanism in which the adjustable stopper mechanism is also integrated. The C clamp (58) controls the angular motion of the pawl link plate (60) and the pedal plate (56), once the pawl (44) disengages from the ratchet (42). This causes the upper column tube assembly (10) to unlock from the lower column tube assembly (30). Now, the steering column (100) can be tilted towards/away from the driver as per the ergonomic requirement. Once the foot plate (52) is released, the pawl support compression springs (48) pull the pawl (44) back for engaging with the ratchet (42), thereby the steering column (100) is locked. Simultaneously, the pedal spring (66) helps in returning of the adjustable stopper mechanism to contact with the adjustable cum stopper gusset (50).

Thus in the present invention, the adjustable stopper mechanism is designed to reduce the radial play and slippage of the steering column (100) when higher push pull force is applied on the steering wheel. This linkage mechanism is unique since both four bar mechanism and the adjustable stopper mechanism are integrated therein. The mechanism is robust in design as it uses the double sided ratchet and pawl mechanism (40) with the pawl actuating linkage mechanism located at the centre. Also, it offers benefit of easy installation across different vehicle platforms.

Advantages of the invention:

1. The tilting mechanism of the present invention is better equipped than competition with lesser no of components and lesser radial play.
2. The mechanism of the present invention provides fail safe positive lock mechanism and robust design with the double sided ratchet and pawl mechanism (40) that avoids steering column angular play which will enhance customer satisfaction.
3. Using the mechanism of the present invention, complaints like gas spring failure while customer abuse and warranty claims are prevented.
4. The present invention adjusts the angular position of the steering column by actuating the double side pawl with linkage mechanism which is designed within the packaging space available across different vehicle platforms.
5. The linkage mechanism is designed to assist the customer in tilting the steering column, lock and unlock the steering column (100) at multiple positions without any slippage and reduced radial play.
6. The mechanism of the present invention is modular in design for easy installation and flexible integration across different vehicle platforms which reduces Steering column Assembly cycle time.

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 scope of the invention.