COMPLETE AFTER PROVISIONAL LEFT ON 14/8/06
FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
A BI-DIRECTIONAL CLUTCH ASSEMBLY;
LARSEN & TOUBRO LIMITED, A COMPANY INCORPORATED UNDER THE COMPANIES ACT, 1956, WHOSE ADDRESS IS L&T HOUSE, BALLARD ESTATE, MUMBAI - 400 001, MAHARASHTRA, INDIA
THE FOLLOWING SPECIFICATION
PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

FIELD OF THE INVENTION
The present invention relates to a bi-directional clutch particularly to a bidirectional overrunning clutch to operate switch disconnector fuse. BACKGROUND OF THE INVENTION
Overrunning clutches generally permit the transmission of high torques in a small design space and are used for example for freewheeling and switching operations and also as back-run stops. The torque requirement in every ON-OFF and OFF-ON operation of the motor operator is up to the toggle point of the switch disconnector fuse/switching device. After toggle point there is a free running zone in every ON-OFF and OFF-ON operation. During this free running zone speed of the motor suddenly increases which results in an overall increase in the inertia torque of the total gear train. This increased inertia torque tries to drive the main shaft of the said switch beyond its dead positions due to this motion there is a damage to the components of the motor operator. Numerous overrunning clutches have been shown in prior art drive systems. However most of them have no provision for complete disengagement between the driving and the driven members during the overrunning operation. The prior art devices, which do include means for disengagement between the driving and the driven members are constructed so as to be responsive only to predetermined increases in rotational speeds. These prior art devices are therefore limited since disengagement and free overrunning is possible only after a substantial increase in centrifugal speed.
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US 3340972 describe a (bi-directional) pawl clutch including at least one pawl operatively connected to a cam. The mass centroid of the pawl is movable from its first position wherein the pawl is operatively engaged to a second radically outward position, as the pawl rides up a driven cam surface. At the second radically outward position, the centrifugal force acting at the mass centroid is sufficiently increased to overcome a biasing means tending to hold the pawl in engagement with the driven cam surface. This clutch disengages drive after a particular designed rotational speed is attained or in other way the aforementioned clutch is speed dependent. Pawls get lifted due to the centrifugal force acting on the pawls.
Therefore a drawback of the bi-directional pawl clutch assembly is that a particular speed is required for overrunning to begin and the disengagement of the driving member from the driven member to take place. Bi-directional overrunning clutch assemblies typically employ an inner race an outer race, and a plurality of rollers as the engagement mechanism disposed therebetween. The bi-directional overrunning clutches generally known in the art are typically designed to be self-actuating. However, these self-actuating bidirectional overrunning clutches are relatively mechanically complex and have certain physical limitations and drawbacks. For example, the inner and outer race must rotate relative to one another over a relatively large angular distance between an engaged position in one rotational direction and the engaged position in the opposite rotational direction.
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Moreover, the self-actuating bi-directional clutches known in the art generally suffer from the disadvantage that they cannot be selectively engaged in an efficient manner and there is a difficulty in the reengagement of the gears. So, there remains a need in the art for a bi-directional clutch that is position dependent and can be engaged and disengaged automatically at achieving particular positions of the drive. Furthermore, there remains a need in the art for a controllable bi-directional overrunning clutch assembly that can provide both torque translation in either rotational direction. In addition, there remains a need in the art for a bi-directional clutch assembly that can be effectively shifted between various operational modes without jamming of the engagement mechanism or other failures occurring at the interface between the races of the clutch assembly.
Further in bi-directional overrunning clutches after completing 90 degrees of rotation the driving member or the drive needs to be disengaged from the driven member. But due to improper disengagement of the driving and driven members, the driving shaft due to inertia the gear system gets jammed and the driving member gets twisted. So therefore there is a need for a clutch assembly that can effectively and efficiently disengages the clutch and avoid jamming of the gear system and twisting of the driving shaft.
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SUMMARY OF THE INVENTION
An object of the present invention is to completely disengage the driving system from the driven system of a switch with the help of the bi-directional overrunning clutch that is position dependent.
Another object of the present invention is to provide an improved clutch operable for free overrunning between the driving and the driven clutch members. According to the most preferred embodiment of the present invention A bidirectional clutch assembly for switches or the like, comprises a ratchet having atleast two teeth, at least two pawls among which at least one pawl engaged at a time with one of the teeth provided on the ratchet, a middle plate and the ratchet coupled with a main shaft; and a lifting pin for each pawl adapted on the middle plate to enable the pawl to get engage and disengage with said teeth provided on the ratchet at a predetermined angular position with respect to the main shaft enabling the elevation of one of the pawl engaged with the teeth and the ratchet when said angular position of the main shaft is achieved thereby disconnecting a driving system from a driven system.
According to another embodiment of the present invention a conical insert is mounted on the main shaft above the pawl disc. The conical insert is mounted in such a way that axial downward movement of the conical insert is allowed. Downward movement of the said conical insert causes the outward rotation of the pawls about its respective pivot. This outward rotation of the pawls results in the disengagement of the driven pawls and driving ratchet with gear train. This accomplishes manual operation of the clutch to any desired angular position.
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The bi-directional clutch assembly completely disengages the driving and the
driven system after 90 degrees of rotation of the shaft thereby transmitting the
torque in one direction and overrunning in the opposite direction. This complete
disengagement takes place for two positions of the main shaft.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 illustrates the exploded view of the main shaft assembly according to
the present invention.
Figure 2 illustrates the sectional view of the main shaft assembly according to the
present invention.
Figure 3 illustrates the plan view of the overrunning mechanism. Torque is
transmitted in clockwise direction only and overrunning in counterclockwise
direction as main shaft is in off condition according to the present invention.
Figure 4 illustrates the plan view of the overrunning mechanism. Torque is
transmitted in counterclockwise direction only and overrunning in clockwise
direction as main shaft is in on condition according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
In general aspect of the present invention a bi-directional clutch assembly for the
switches or the like comprises a ratchet having atleast two teeth, at least two
pawls among which at least one pawl engaged at a time with one of the teeth
provided on the ratchet, a middle plate and the ratchet coupled with a main shaft,
and a plurality of lifting pins adapted on the middle plate. The plurality of lifting
pins are adapted on the middle plate so as to enable the pawl to get engage and
disengage with said teeth provided on the ratchet wherein the plurality of lifting
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pins are positioned at a predetermined angular position with respect to the output shaft in such a way that the pawl gets elevated when the said angular position is achieved by the main shaft.
In the following detailed description of the preferred embodiments of the present invention reference is made to the accompanying fig 1 and fig 2, which in conjugation with this detailed description, illustrates and describes the exploded and sectional view of the bi-directional clutch assembly. The present invention is based on the ratchet and pawl mechanism for positioning the main shaft (26) and overrunning of the gear train (not shown) after the desired angular position of the main shaft (26) is achieved.
The clutch assembly comprises of a main shaft (26) which serves as the essential supporting element and to which is attached the other elements of the bi-directional clutch assembly. The final gear (30) of a motor driven gear train is mechanically connected to a ratchet (10) through the coupling (12). The ratchet (10) is designed in such a way so as to possess at least two teeth (14). However, the ratchet (10) may be designed in such a way so to have a number of sets of teeth (14) as per the requirement and each set may consist of one or plurality of teeth (14). The teeth (14) of the said ratchet (10) are made in such a way that one set of teeth (14) transmits the motion in clockwise direction and another set transmits motion in counterclockwise direction. Middle plate (24) houses a plurality of lifting pins (22) (hereafter referred as pawl lifting pins) preferably two fixed on the middle plate (24). A conical insert (28) is also mounted on the main shaft (26) above the pawl disc (18).
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Atleast two pawls (16a and 16b) are pivotally mounted on a pawl disc (18) with a spring arrangement (20) tending to hold the pawls (16a and 16b) in engagement with the teeth (14) of the ratchet (10). The pawls (16a and 16b) are mounted on the pawl disc in such a manner that atleast one of the pawl (16a and 16b) remains engaged with one of the teeth (14) provided on the ratchet (10) as shown in fig 3 and fig 4. Provision is made in such a way that each pawl (16a and 16b) transmits the torque in one direction depending on the mounting with respect to the ratchet teeth and overruns in the opposite direction. Pawl lifting pins (22) are fixed on the middle plate (24) at a desired angular position with respect to the main shaft (26). As soon as the desired angular position of the main shaft (26) is achieved the pawl lifting pins (22) lifts the pawls engaged on the teeth (14) of the ratchet (10) thereby disconnecting the driving system from the driven system and overrunning the gear train without increasing the stress level of the system.
In the bi-directional clutch assembly the main shaft (26) is marked at an 'ON' position and an 'OFF' position. The 'ON' and 'OFF' operation of a bi-directional overrunning clutch assembly will now be described according to the present invention with reference to the fig 3 and fig 4. As described earlier the pawl lifting pins (22) are fixed on the main plate (24) at a desired angular position with respect to the main shaft (26) for lifting each of the pawls when the desired angular position of the shaft is achieved. The pawls (16a and 16b) are continuously engaged with the teeth (14) provided on the ratchet (10). Provision is provided in such a way that for each of the pawl a pawl lifting pin is provided.
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The main shaft (26) starts rotating and as the main shaft (26) reaches the 'OFF' position, the pawl lifting pin (22) provided for lifting the pawl (16b) and located on the opposite side of the 'OFF' position lifts the pawl (16b) thereby enabling the gear overrun in counter-clockwise direction. The torque is transmitted in the clockwise direction and the overrunning in counter-clockwise direction as described in fig 3. When the main shaft (26) reaches the 'OFF' position the pawl (16a) located on the same side as that of the 'OFF' position as is continuously engaged with the teeth (14) of the ratchet stops the main shaft (26) from rotating further thus the driving system is disengaged automatically with the driven system.
If after completion of one quarter of the rotation i.e., achieving the 'dead position' after 90 degrees of rotation, the clutch does not disengages the driving system from the driven system the shaft will rotate further to 90 degree thereby resulting in jamming of the system and chances are that the gear system would break and the main shaft (26) to get twisted. As soon as one quarter of the rotation is achieved i.e., the main shaft (26) reaches the 'OFF' position the pawl lifting pin (22) provided on the opposite side of the 'OFF' position lifts the pawl (16b) which is engaged to the teeth (14) of the ratchet (10) thereby resulting in disengaging the pawl (16b) from the teeth (14) of the ratchet (10) and enabling the overrunning of the gear train coupled to the ratchet (10). Similarly as described above, as the main shaft (26) reaches the 'ON' position, the pawt (16b) located on the same side of the 'ON' position and engaged with the teeth (14) of the ratchet (10) stops the main shaft from rotating further thus
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again disengaging the driving system from the driven system. At the same time the pawl lifting pin (22) provided on the opposite side of the 'ON' position lifts the pawl (16a) provided therein thereby resulting in disengaging the pawl (16a) from the teeth (14) of the ratchet (10) and enabling the overrunning of the gear train coupled to the ratchet (10). Thus the torque is transmitted in the counterclockwise direction and the ratchet and the coupling enable the gear overrun in clockwise direction as described in fig 4.
According to another embodiment of the present invention a conical insert (28) is mounted on the main shaft (26) above the pawl disc (18). The conical insert (28) is mounted in such a way that axial downward movement of the conical insert (28) is allowed. Downward movement of the said conical insert (28) causes the outward rotation of the pawls about its respective pivot. This outward rotation of the pawls (16) results in the disengagement of the driven pawls and driving ratchet with gear train. This accomplishes manual operation of the clutch to any desired angular position. Further the axial downward movement of the conical insert (28) can be achieved by various means i.e., by pressing manually or through a cam mechanism or through a slide mechanism. In addition, in this new arrangement, angular position of the rotating main shaft can be preciously controlled. Also stress level in the components is reduced due to achievement of the bi-directional overrunning mechanism after the particular angular position of the main shaft (26) in each direction.
Thus it is apparent from the present invention provides an efficient bidirectional overrunning clutch which is position dependent which effectively disengages the
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driving member from the driven member without increasing the stress level of the system.
Also it is understandable from the present invention the clutch disengages and engages selectively as a quadrant of rotation of the main shaft of the drive is achieved thereby effectively transmitting the torque in one direction and overrunning in opposite direction and also to avoid jamming of the gear system. The foregoing description of the invention has been set for merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to person skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.
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WE CLAIM:
1. A bi-directional clutch assembly, comprising;
a ratchet having atleast two teeth;
at least two pawls among which at least one pawl engaged at a time with
one of the teeth provided on the ratchet;
a middle plate and the ratchet coupled with a main shaft; and
a lifting pin for each pawl adapted on the middle plate to enable the pawl
to get engage and disengage with said teeth provided on the ratchet at a
predetermined angular position with respect to the main shaft enabling the
elevation of one of the pawl engaged with the teeth and the ratchet when
said angular position of the main shaft is achieved thereby disconnecting a
driving system from a driven system.
2. The bi-directional clutch assembly as claimed in claim 1, wherein the ratchet rotates in clockwise direction and in counter clockwise direction.
3. The bi-directional clutch assembly as claimed in claim 1, wherein the pawls are pivotally mounted on a pawl disc with a spring arrangement in such a manner so as to engage the pawl with the ratchet teeth.
4. The bi-directional clutch assembly as claimed in claim 1, wherein the main shaft has 'ON' and 'OFF' positions.
5. The bi-directional clutch assembly as claimed in claim 1 and 4, wherein as the main shaft reaches 'OFF' position, the pawl engaged with the teeth of the ratchet and located on the opposite side of the 'OFF' position gets elevated by the lifting pin provided therein thereby enabling the torque to
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be transmitted in clockwise direction and enabling the overrun in counterclockwise direction.
6. The bi-directional clutch assembly as claimed in claim 1 and 4, wherein as the main shaft reaches 'ON' position, the pawl engaged with the teeth of the ratchet and located on the opposite side of the 'ON' position gets elevated by the lifting pin provided therein thereby enabling the torque to be transmitted in counter-clockwise direction and enabling the overrun in clockwise direction.
7. The bi-directional clutch assembly as claimed in claim 1, further comprising a conical insert mounted on the main shaft in such a way that axial downward movement of the conical insert enables the outward rotation of the pawls which in turn results in disengagement of the pawls and the ratchet from a gear train.
8. The bi-directional clutch assembly as claimed in claim 1, wherein the bidirectional overrunning clutch operates in 90 degrees angular rotation of the main shaft or equal to the quarter of a revolution.
9. The bi-directional clutch assembly as herein described and shown in Fig 1,2,3 and 4.
Dated this 14lh day of August 2006
FOR LARSEN & TOUBRO LIMITED
By their Agent

(GIRISH VIJAYANAND SHETH) KRISHNA &SAURASTRI
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ABSTRACT
A bi-directional clutch assembly for switches or the like, comprises a ratchet having atleast two teeth, at least two pawls among which at least one pawl engaged at a time with one of the teeth provided on the ratchet, a middle plate and the ratchet coupled with a main shaft, and a lifting pin for each pawl adapted on the middle plate to enable the pawl to get engage and disengage with said teeth provided on the ratchet wherein the plurality of lifting pins are positioned at a predetermined angular position with respect to the main shaft enabling the elevation of one of the pawl engaged with the teeth and the ratchet when said angular position of the main shaft is achieved thereby disconnecting a driving system from a driven system of the switch.
1 4 AUG2006