DESC:TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to a clutch systems integrated into a gearbox. More particularly, the present invention provides an assembly with mechanical override capability on completion of a predetermined degree of rotational motion in gear box.

BACKGROUND AND THE PRIOR ART
Systems for electrically charging a mechanism spring generally involve either compression or extension of the spring. This is achieved by coupling of a motor to a speed reduction gearbox to generate more torque. This torque is then utilized to drive an external charging member, which delivers force by cam action in order to charge the spring.
Current charging system uses clutch assembly and ratchet system to achieve mechanical cut-off between the gears and the charging shaft once springs are charged fully. Clutch assembly consists of a pawl, pawl link and an extension spring. Pawl is riveted on pawl link. When charging is completed, pawl over rides over roller and hence mechanical cut-off is achieved through rotational movement. Once the energy of mechanism springs is used, pawl engages with the ratchet and ECD is ready for the next operation.
The existing charging system uses rotational movement of clutch assembly to provide mechanical cut-off. This system results in additional fly-off of the pawl and also produces stresses on the rivet which is used to assemble pawl and pawl link. This additional stress results in breakage of the rivet and ultimately results in non-functioning of mechanical cut-off system. The failure can also take place due to shearing off, of the pawl link extension spring. Failure of mechanical cut-off system thus results in continuous running of motor and hence over-heating and burning of motor windings. It also results in damage to teeth of the gears; damage to profile of cam of mechanism.
Such systems are encountered in devices or mechanisms which require a spring to deliver input force for it to deliver output. The effort provided to the system is the charging of the spring (i.e. compressed or extended depending on the type of spring), and the charging operation has to be accomplished electrically.
The override system is essential so as to avoid damage to whichever component in the charging system, be it the motor, the gearbox, the external charging member or the spring to be charged.
US5383818 disclosed an overload clutch limits the transmittable torque moment by permitting an override when a certain compression force is exceeded. For this purpose a drive shaft meshes with a disk provided with a number of holes in which balls are received. The disk has an axial thickness smaller than the diameter of the balls so that the balls can be uniformly exposed to a compression force exerted by a compression spring through a disk or bushing bearing on the balls. The balls cooperate with an entraining cam disk. As long as the torque to be transmitted is smaller than the compression force, the balls engage cam ribs on the entraining disk and transmit the torque. When the input torque exceeds the compression force, the balls override the cam ribs.
Therefore, the present invention provides a clutch assembly operatively integrated into the gearbox, which fundamentally decouples the gearbox output torque from the shaft which delivers the said torque to the external charging member, once the charging cycle is completed. This mechanical override has to be provided so that the external member does not exceed the predetermined degree of rotation which completes the charging operation.

OBJECTS OF THE INVENTION
A basic object of the present invention is to overcome the disadvantages/drawbacks of the known art.

Another object of the present invention is to provide a clutch assembly for mechanical override in gearbox with axial translation so that external member does not exceed a predetermined degree of rotation which completes the charging operation.

Another object of the present invention is to provide an assembly enhancing reliability of system by reducing number of components used.

Another object of the present invention is to provide an assembly with low manufacturing and assembly costs therefore providing an improved life.

These and other advantages of the present invention will become readily apparent from the following detailed description read in conjunction with the accompanying drawings.

SUMMARY OF THE INVENTION
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.
In an aspect of the present invention, there is provided a clutch assembly for mechanical override in a gearbox, said assembly comprising: a gearbox output shaft functionally connected to a gearbox base plate; a ratchet, wherein said ratchet is free to rotate about said gearbox output shaft and is rigidly coupled to a gear stage(s); a pawl base-link assembly comprises a pawl link and a pawl base, wherein said pawl link is mounted on said pawl base; a cutoff spring positioned between said pawl base-link assembly and said ratchet; a cutoff pin riveted on said gearbox base plate; wherein said clutch assembly facilitating mechanical override in said gearbox with axial movement of said pawl base link assembly on completion of a predetermined degree of rotational motion of a driven element.

Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The following drawings are illustrative of particular examples for enabling methods of the present invention, are descriptive of some of the methods, and are not intended to limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description.
Figure.1 illustrates the clutch assembly.
Figure.2 illustrates the arrangement of compressed cutoff spring in clutch assembly.
Figure.3 illustrates the gear output shaft.
Figure.4 illustrates the pawl base-link assembly and the ratchet.
Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure.
Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION OF THE INVENTION
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.
The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.
By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.
Accordingly, present invention provides a clutch assembly for mechanical override in gearbox with axial translation; therefore external member does not exceed a predetermined degree of rotation which completes the charging operation.
The present invention deals with the clutch operation integrated into the gearbox, which fundamentally decouples the gearbox output torque from the shaft which delivers the said torque to the external charging member, once the charging cycle is completed. This mechanical override has to be provided so that the external member does not exceed the predetermined degree of rotation which completes the charging operation.
The present invention encompasses a technique which gives the provision of mechanical override to a torque delivering driving system so as to decouple the driven element from the driver, after predetermined rotational travel. The functional assembly comprises of the following components:
· Gearbox base plate (11)
· Gearbox Output Shaft (12)
· Ratchet (13)
· Pawl Link (14)
· Pawl Base (15)
· Cutoff pin (16)
· Cutoff spring (17)
· Bush (21)

The invention consists of a ratchet (13) which is free to rotate about the gearbox output shaft (12) and is rigidly coupled to the gear stages before it. The pawl base (15) is non-rotatable about the gearbox output shaft (12), but the coupling is such that it allows axial travel of the base (15) along the same shaft (12). The pawl link (14) in turn is firmly mounted onto the pawl base (15). The cutoff spring (17) is a compression spring situated between the pawl base-link assembly (14-15) and the ratchet (13).
The cutoff pin (16) is riveted to the gearbox base plate (11) which also houses the bush (21) in which the gearbox output shaft rotates without restraint. The driver torque originates from the electrical motor, and is transmitted via the gearbox sequentially amplifying the torque through the stages (18).
At the commencement of the charging operation, the torque transmitted by the gearbox is transmitted directly to the ratchet (13). Due to the particulars of assembly and the component mounting positions at the beginning of charging, the cam action of the cutoff pin (16) against the flat surface of the pawl base (15) causes the compression of the cutoff spring (17). This forces the pawl base (15) and hence the pawl link (14) is towards the ratchet (13) and causes positive engagement between the pawl link (14) and the tooth of the ratchet (13).
Due to this, the driver torque coming to the ratchet (13) is sequentially transferred to the pawl link (14) and thus, the pawl base (15) and then onto the gearbox output shaft (12), culminating in the torque being delivered to the driven member (19). At the termination of the charging cycle, the location of the cutoff pin (16) is such that on completion of a predetermined angle of rotation of the gearbox output shaft (12), a deliberately placed groove (20) on the pawl base (15) interacts with the cutoff pin (16). This groove provides the pawl base (15) clearance for the expansion of the compressed cutoff spring (17). Since the pawl base-link assembly (14-15) is free to translate along the gearbox output shaft (12) axis, it disengages from the tooth of the ratchet (13). Now, the driver ratchet (13) is decoupled from the driven pawl link (14) which is the mechanical override clutch action integrated into the gearbox.
Once, the mechanism / device operates it causes the discharging of the spring and a release of the external charging member. The said member is rigidly coupled to the gearbox output shaft (12) and hence the pawl base (15) which rotates partially. This causes the cam action of the cutoff pin (16) against the groove (20) on the pawl base (15), again pushing it towards the base (15) and the link (14) towards the ratchet (13). The initial position of engagement is attained again and the charging cycle can commence thereafter.
ADVANTAGES
· The disclosed system replaces existing rotational mechanical override system with axial translation clutch assembly
· Elimination of highly stressed, low strength components
· Less number of components to enhance reliability of system
· Positive engagement during torque transmission by strong cutoff pin cam action
· Low manufacturing and assembly costs with improved life

NOVEL FEATURES:
· Design of components used in disclosed patent to achieve mechanical cut-off when mechanism is fully charged.
· Axial movement of pawl to achieve this mechanical cut-off, therefore overcoming drawbacks faced in current system of mechanical cut-off.
· Design facilitates use of individual components as single unit providing higher strength & reliability in comparison with highly stressed low strength components used in previous arts.
· Positive engagement during torque transmission is based on reliable cutoff pin cam action and not on weaker spring bias.
,CLAIMS:1. A clutch assembly for mechanical override in a gearbox, said assembly comprising:
a gearbox output shaft functionally connected to a gearbox base plate;
a ratchet, wherein said ratchet is free to rotate about said gearbox output shaft and is rigidly coupled to a gear stage(s);
a pawl base-link assembly comprises a pawl link and a pawl base, wherein said pawl link is mounted on said pawl base;
a cutoff spring positioned between said pawl base-link assembly and said ratchet;
a cutoff pin riveted on said gearbox base plate;
wherein said clutch assembly facilitating mechanical override in said gearbox with axial movement of said pawl base link assembly on completion of a predetermined degree of rotational motion of a driven element.
2. The assembly as claimed in claim 1, wherein said pawl base is non-rotatable in relation to said gearbox output shaft, whereby allowing axial travel of said pawl base along said gearbox output shaft.
3. The assembly as claimed in claim 1, wherein the driver torque is generated using an electrical motor, and is transmitted through a gearbox.
4. The assembly as claimed in claim 1, wherein compressing said cutoff spring due to cam action of said cutoff pin against the surface of said pawl base, facilitating connection between said pawl link and said ratchet, in starting of the charging operation.
5. The assembly as claimed in claim 3 and claim 4, wherein transmitting the torque from said gearbox to said ratchet, thereby said ratchet sequentially transferring the torque to said pawl base link assembly subsequently to said gearbox output shaft, and therefore culminating in the torque is being delivered to said driven element.
6. The assembly as claimed in claim 1, wherein said pawl base having a groove providing a clearance for the expansion of said cutoff spring.
7. The assembly as claimed in claim 1 and claim 6, wherein said groove interacts with said cutoff pin on completion of a predetermined angle of rotation of said gearbox output shaft, therefore decoupling said ratchet from said pawl base-link assembly resulting into discharging of said cutoff spring and decoupling of said driven element, during termination of charging operation.
8. The assembly as claimed in claim 1, wherein said cutoff spring is a compression spring.
9. The assembly as claimed in claim 1, wherein said gearbox base plate accommodating a bush to facilitate rotation of said gearbox output shaft without restraint.