IMPROVED STEERING MECHANISM FOR OFF-HIGHWAY VEHICLE
I. Field of the invention:
The field of the present invention is related to proposing a novel and improved steering mechanism for Off-highway vehicles towards maximizing the load lifting capacity, particularly in the steered condition, more particularly in case of cranes, wherein the increase in lifting capacity is obtained by a tilt in the Axis of Articulation (AA) from the vertical line, by certain small angles.
II. State of the art in the field:
In automobile industry, whenever a conventional highway vehicle like car or truck etc. or an Off-highway vehicle like crane, particularly mobile crane, is designed and manufactured, the vehicle has to go through several quality tests and satisfy several standards. It is important for every type of vehicle that it must have high load lifting/carrying capacity as well as effective stability thereof, according to the pre-decided targets for a particular design and model.
There are several conventional methods for increasing the load lifting/carrying capacity of an Off-highway vehicle, particularly of a crane in its steered condition. The most common method is to provide a longer wheel base to the vehicle. Another method, known for the same purpose is to provide a movable counterweight, which is capable of moving in a direction opposite of the steer direction, ensuring a counterbalance and thereby increasing the load lifting/carrying capacity.
Actually the load lifting/carrying capacity of a vehicle, particularly of an Off-highway vehicle, and more particularly of a crane/mobile-crane, is directly related to the vehicle steering mechanism. In a car or other conventional highway vehicle like a truck, the steering is achieved by swiveling the angle of the front wheels relative to the body (Figure-1). The wheels rotate around their own swivel axis, and the swivel is controlled by a simple steering mechanism. But in cases of Off-highway vehicles like cranes, the vehicle body itself swivels about an Articulation Axis to achieve steer (Figure-2).
Off-highway vehicles are steered by articulation about a central axis (Articulation axis). The vehicle's body can be considered in two halves, Front body and Rear body, wherein each half with a single fixed axle and able to rotate with respect to the other around and articulation Axis (AA).
The conventionally a single vertical Articulation Axis is used in every type of Off-highway vehicles, including the Cranes. Such conventional mechanism of steering using single vertical Articulation Axis has certain limitations on the vehicle's load lifting/carrying ability and on the vehicle's ability to maneuver over uneven surfaces.
Ideally it is expected that an Off-highway vehicle like crane/mobile-crane must lift/carry a pre-calculated/targeted load in its straight condition as well as in its steered condition. At the same time, it is always a target to design an Off-highway vehicle like a crane/mobile-crane that it should have almost equal load lifting/carrying capacity in its straight condition as well as in its steered condition. But till date, achieving such expected load lifting/carrying standards for an Off-highway vehicle like a crane/mobile-crane is a challenge to the industry. Conventionally it is analyzed that while the load lifting/carrying capacity of a
crane, with conventional vertical Articulation Axis, is equal or more than the pre-calculated design targets in its straight condition, the load lifting/carrying capacity is considerably inadequate in the steered condition of the vehicle's body (when the crane is steered to the right or the left).
Several modifications have been made to the basic design and structural features of the Articulation Axis (AA) to improve the performance of the vehicle.
US Patent No. 4236591 describes a modification to the Articulation axis to permit a oscillation in addition to articulation about the (AA). This helps the better traverse uneven ground and change attachments to the vehicle. However, the (AA) is defined as a vertical axis therein.
US Patent 4580797 provides for additional rotational axes and adjustments so that the vehicle can adjust to terrain irregularities while keeping the cab in a stable position. The two vehicle halves rotate in a horizontal plane for steering, about a vertical axis. There is no provision for deliberately moving this plane away from the vertical line.
US Patent 5180028 provides for a non-vertical axis of rotation for attachments to an Off-highway vehicle. This permits the attachments (like scrapers) to attack the ground at an angle that is different from the angle set by the vehicle. However the vehicle's steering Articulation Axis is kept vertical at all times.
US Patent 7252203 highlights the importance attached to mechanisms that increase the load lifting capacity of mobile cranes. In this patent, a technique of effectively increasing the load lifting capacity by increasing the counterweight, proportional to the load, is taught.
III. Object of the invention (Problem & Solution):
In light of the aforementioned background of the invention it is seriously realized that the Off-highway vehicles, particularly cranes/mobile-cranes, should have better and virtually equal load lifting/carrying ability in its straight condition as well as in its steered condition; and the said load lifting/carrying capacity of the said crane/mobile-crane or Off-highway vehicle must follow the pre-calculated design targets of the said crane/mbbile-crane or Off-highway vehicle towards ensuring better load handling in the safest manner.
Therefore the present invention is a novel effort to propose a new and improved steering mechanism for Off-highway vehicles, particularly for cranes/mobile-cranes, towards maximizing the load lifting/carrying capacity, particularly in the steered condition; wherein the increase in lifting/carrying capacity is obtained by a tilt in the Axis of Articulation (AA) away from the vertical line, by certain small angles.
The principle objective of the present invention is to propose a novel improved steering mechanism for Off-highway vehicles, particularly in cranes/mobile-cranes, and the concept of said mechanism is termed herein as "Articulation Axis Tilt (AAT)".
Another essential objective of the present invention is to propose a tilt of certain small angle to the Articulation Axis of an Off-highway vehicle, particularly a crane/mobile-crane, away from the vertical line, with the top of the axis shifted towards the rear body part of the said vehicle.
Further another objective of the present invention is to propose a novel Articulation Axis, based on the concept of AAT, wherein the Articulation Axis tilt
is preferably in the range of zero to six degrees, away from the vertical line towards achieving the pre-calculated vehicle's design target of its full load lifting/carrying capacity, particularly in steered condition of the vehicle; and wherein the degree of said tilt (AAT) depends upon certain pre-calculated load lifting/carrying design target for the Off-highway vehicle, particularly for the crane/mobile-crane.
Further another objective of the present invention is to propose a novel method, based on AAT, to achieve several features associated to Off-highway vehicles, particularly to cranes/mobile-cranes, namely:
(i) Higher load lifting/carrying capacity in the straight condition as well as in the steered condition of said vehicle;
(ii) Better self-aligning feature and self-stability of the said vehicle, particularly during the motion with load, and more particularly during the steered motion with load;
(iii) Better and uniform distribution of the overall stress over the entire body of the said vehicle, particularly when the said vehicle loaded at one side during an articulated lift.
IV. Statement of Invention:
Accordingly the present invention provides an improved Articulation Axis with a tilt of certain small degrees, preferably for applying in the Off-highway vehicles and more preferably for applying in the cranes/mobile-cranes towards achieving more balanced steering in such vehicles, particularly in view of achieving a pre-calculated vehicle's design target of maximized load lifting/carrying capacity; wherein the proposed Articulation Axis of said
crane/mobile-crane/Off-highway vehicle is characterized by certain tilt in such a manner that the top of the said Axis inclines towards the rear body part of the said vehicle, and makes a very small slope with the vertical line, and wherein the angle of the said proposed tilt of Articulation Axis is preferably in the range of zero to six degrees to achieve the optimum lift capacity and maximum stability of the vehicle's body, especially in its steered condition. The present invention also provides a novel method, based on Articulation Axis Tilt (AAT), to achieve several features associated to Off-highway vehicles, particularly to cranes/mobile-cranes, namely:
(i) Higher load lifting/carrying capacity in the straight condition as well as in the steered condition of said vehicle;
(ii) Better self-aligning feature and self-stability of the said vehicle, particularly during the motion with load, and more particularly during the steered motion with load;
(iii) Better and uniform distribution of the overall stress over the entire body of the said vehicle, particularly when the said vehicle loaded at one side during an articulated lift.
V. Detailed description of the invention with reference to the drawings:
The present invention very specifically proposes a new Articulation Axis with slight tilt for Off-highway vehicles, particularly for cranes/mobile-cranes, wherein the said tilt is particularly achieved by positioning and installing a thick and strong straight Articulation Shaft in such a way that the top of the said Shaft inclines towards the Rear body of the vehicle, away from the vertical line creating very small slope with the vertical line. For mounting this thick and strong straight
Articulation Shaft between the Front and Rear bodies of the Off-highway vehicle like crane/mobile-crane, each pivot plate of the Front Body and Rear Body of said vehicle or crane/mobile-crane is created with one slot, wherein the said slots on the said pivot plates are positioned and created in such a manner that they are not only very much compatible to each other as well as to the said Articulation Shaft, but the imaginary straight line passing through these slots creates a slightly tilted axis, that is the proposed tilted Axis of Articulation (AA) herein.
The whole concept of designing the Articulation mechanism for an Off-highway vehicle like a crane/mobile-crane mainly includes designing of the straight Articulation Shaft; designing of upper and lower pivot plates with single slot each on front body and rear body of the said vehicle/crane; and creation of four slots at certain angles compatible to each other and to the Articulation Shaft to be accommodated therein towards creation of a tilted Articulation Axis, away from the vertical line. This whole concept herein is termed as "Articulation Axis Tilt (AAT)".
Once the Articulation Shaft is placed and installed in the slots made in the pivot plates of the front body and Rear body of the said vehicle or said crane/mobile-crane, the vehicle/crane can be operated by the operator for lifting/carrying the virtually equal quantity of load which is pre-calculated and already targeted for that model of the said vehicle/crane, even in its straight as well as in steered conditions.
The present invention and the proposed steering mechanism can be understood better with the help of certain drawings labeled with numerals, attached herein. Brief description of the drawings is as follows:
Figure 1: It represents a schematic view of steering in case of a conventional highway vehicle like car or a truck etc.
Figure 2: It represents a schematic view of steering in case of an Off-highway vehicle, particularly a crane/mobile-crane characterized by two halves of the whole structural body as front body and rear body joined together at the common Articulation Axis , wherein the drawing depicts the straight and the steered vehicle conditions.
Figure 3: It represents a schematic view of the proposed tilted Articulation Axis between the front body and the rear body of an Off-highway vehicle, particularly in case of a crane/mobile-crane, wherein the said tilted Articulation Axis is created at a small angle away from, the imaginary vertical line, particularly with the help of tilted slots of the pivot plats accommodating the proposed Straight Articulation Shaft.
A conventional highway vehicle 1, like a car or truck, as schematically depicted in Figure-1, has usually one rigid undivided body, comprising of wheels at four positions, two at the front of the vehicle's body (shown by 2 or 2') and two at the rear of the body. Front wheels are joined with an axel 3 whereas the rear wheels are associated with another axel 5. Usually the front wheels in their straight condition, as represented by 2', rotated around their own swivel axis and finally reaches to the steered condition, as shown by 2. The relative angle of swivel is controlled by a steering mechanism.
In case of Off-highway vehicles, particularly in case of cranes/mobile-cranes (Figure-2), the vehicle's body can be considered in two halves, front body 6 and rear body 7. The front body 6 of said Off-highway vehicle or crane/mobile-
crane rests on a set of wheels 8 or 8', joined together by a single axel, 9 (or 9'); while the rear body 7 of the said vehicle/crane rests on a set of wheels 11, joined together by a single axel 12. The front body 6 and the rear body 7 are suitably connected together at a central position 10 with the help of an articulation mean, a accommodated with certain slots of the pivot plates (not depicted in the drawing), at the position 10. Conventionally an Articulation Shaft, which is usually a thick, strong and straight rod like structure is so fixed with the slots of the pivot plates of front body 6 and the rear body 7 of the said vehicle at position 10, that the two halves 6 and 7 of the said vehicle are able to rotate freely with respect to another around the said Articulation Shaft or any state-of-the-art articulation mean. The said Articulation Shaft fitted with the suitable slots at position 10, creates an imaginary line which is conventionally a vertical line and till date this vertical line itself is considered as the Articulation Axis of an Off-highway vehicle, particularly a crane/mobile-crane.
Actually according to Figure-2, the front body shown by 6' and rear body 7, collectively represent the straight condition of an Off-highway vehicle, particularly a crane/mobile-crane. When the front wheels 8' on axel 9' of front body 6', in the straight condition of the said vehicle, are directed to rotate around their own swivel axis, supported by a steering mechanism (usually similar as in the conventional highway vehicles like cars and trucks), they bring the front body 6' to a new position 6, respectively changing their own position to 8 and the axel position to 9. Now the front body 6 and the rear body 7, collectively represent the steered condition (left or right) of the Off-highway vehicle, particularly a crane/mobile-crane, wherein the rear body 7 is considered articulated with respect
to front body 6 about an Articulation Axis (conventionally a vertical axis ) at position 10.
Figure-3 clearly represents a schematic view of the proposed tilted Articulation Axis 14, which is not in the same line as the vertical line 13. The proposed Articulation Axis 14 is tilted in such a way that the top of this axis points towards the rear body 7 of the Off-highway vehicle, particularly a crane/mobile-crane. Usually the angle of tilt 15 is selected from a preferable tilt-range between zero degree to six degrees, depending upon the optimum pre-decided target for a particular model of an Off-highway vehicle like crane/mobile-crane towards its load lifting/carrying capacity in its straight as well as steered conditions.
According to the schematic Figure-3, Front body 6 comprises of horizontal pivot plate(s), preferably two in number, one as the upper pivot plate 16 and another as lower pivot plate 18. Similarly the rear body 7 comprises of horizontal pivot plate(s), preferably two in number, one as the upper pivot plate 17 and another as lower pivot plate 19. The front body 6 and the rear body 7 are connected together at position 10, shown by a schematic rectangular box in broken line. Each horizontal pivot plate, 16, 17, 18 and 18 herein comprises one slot, not shown herein, which is not vertical but is created at certain angles with the vertical line 13. The pivot plate 16 comes above 17 and similarly pivot plate 18 comes above 19, and therefore the four slots of these four pivot plates get arranged in a particular imaginary straight line 14, which is the proposed tilted Articulation Axis. Thus each of the said four slots is created on its respective horizontal pivot plate in such a way that the imaginary straight line 14 passing through them, that is the proposed Articulation Axis herein, makes a particular
small angle of tilt 15 with the vertical line 13. The slot of horizontal pivot plate 16, is preferably more tilted (makes bigger angle with the vertical line 13) towards the rear body 7 than the slot of horizontal pivot plate 17 (it makes smaller angle with the vertical line 13). Similarly it is preferably expected that the slot of horizontal pivot plate 19, is preferably more tilted (makes bigger angle with the vertical line 13) towards the front body 7 than the slot of horizontal pivot plate 18 (it makes smaller angle with the vertical line 13). The Articulation Shaft, preferably as a straight and thick rod like structure, is accommodated in the said slots of the said horizontal pivot plates 16, 17, 18 and 19, it simply occupies its position coming in the line of tilted Articulation Axis 14. The whole mechanism comprising of designing and manufacturing of said horizontal pivot plates, their slots herein, the Articulation Shaft, and the tilted Articulation Axis 14 away from the vertical line 13 by an angle of tilt 15, is collectively defined herein as "Articulation Axis Tilt (AAT)".
VI. Scope and/or ambit of the invention:
Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such modifications can be made without departing from the spirit of scope of the present invention as defined.

Claim:
1. An improved steering mechanism for Off-highway vehicles, particularly
for cranes/mobile-cranes, comprising of an improved articulation mean at
central position 10 between front body 6 and rear body 7 of the said
vehicle, wherein the said articulation mean comprises of improved
horizontal pivots 16, 17, 18 and 19 with single slot each; wherein said slots
are characterized firstly by .their creation on their respective horizontal
pivot plate at certain angle with the vertical line 13 and secondly by
accommodation of the Articulation Shaft in the same tilted line of
Articulation Axis 14; and wherein the concept of said mechanism, termed
herein as "Articulation Axis Tilt (AAT)", is characterized by a tilt in the
Axis of Articulation (AA) 14 of the said vehicle away from the vertical
line 13 by a particular angle of tilt 15; and wherein the said mechanism is
further characterized by:
(i) Higher load lifting/carrying capacity in the straight condition as well as in the steered condition of said vehicle;
(ii) Better self-aligning feature and self-stability of the said vehicle, particularly during the motion with load, and more particularly during the steered, motion with load; and
(iii) Better and uniform distribution of the overall stress over the entire body of the said vehicle, particularly when the said vehicle loaded at one side during an articulated lift.
2. An improved steering mechanism for Off-highway vehicles, particularly
for cranes/mobile-cranes, as claimed in claim 1, wherein the said vehicle
comprises of a tilted Articulation Axis 14, away from the vertical line 13 by an angle of tilt 15.
3. An improved steering mechanism for Off-highway vehicles, particularly for cranes/mobile-cranes, as claimed in claim 1, wherein the tilt in the Articulation Axis 14 is such that the top of the axis 14 is inclined towards the rear body 7 of the said vehicle.
4. An improved steering mechanism for Off-highway vehicles, particularly for cranes/mobile-cranes, as claimed in claim 1 and 3, wherein the angle of tilt 15 between vertical line 13 and the Articulation axis 14 is preferably in a range of zero degree to six degrees.
5. An improved steering mechanism for Off-highway vehicles, particularly for cranes/mobile-cranes, as claimed in claim 1, 3 and 4, wherein the said angle of tilt 15 depends upon certain pre-calculated load lifting/carrying design target for the said vehicle, particularly for the crane/mobile-crane, and more particularly depends on the pre-calculated vehicle's design target of its full load lifting/carrying capacity in steered condition of the vehicle.
6. An improved steering mechanism for Off-highway vehicles, particularly for cranes/mobile-cranes, as claimed in claim 1, wherein the proposed mechanism based on "Articulation Axis Tilt (AAT)" mainly comprises of designing and manufacturing of an improved articulation mean consisting of said horizontal pivot plates, their slots herein at certain angles with the vertical line 13 and the Articulation Shaft.7. An improved steering mechanism for Off-highway vehicles, particularly for cranes/mobile-cranes, as substantially as herein described and illustrated in the figures of the accompanying drawings.