Optical window protective shutter mechanism

A visor-like, protective hood assembly consisting of a segmented shutter for covering an optical window and including three hemispherical shutter segments of increasing radii and pivoted about a common pivot for relocation between a retracted, open and nested relation and an extended, closed position. A drive motor, coupled with a Geneva mechanism, directly and intermittently drives the outermost shutter segment, and trailing edge lips on each segment engage with and respectively drive the intermediate and inner segments to their fully extended, closed positions in a protective relation over the window.

BACKGROUND OF THE INVENTION 
This invention relates generally to a novel technique for covering and 
thereby protecting optical windows by the use of a visor-like and 
segmented protective assembly. 
The use of a two or more part-segmented cover, shutter or other type 
assembly of a hollow, spherical configuration and which is pivoted about a 
common pivot point to be moved between a closed, nested position relative 
to each other and an extended, open position is broadly old, as is 
evidenced, for example, in a British Pat. No. 1,350,895, issued July 27, 
1971 and, further, as shown in U.S. Pat. Nos. 1,806,366, issued May 19, 
1931, and 2,384,646, issued Sept. 11, 1945. Moreover, Geneva movements in 
general have, likewise, long been used to provide intermittent or 
sequential motion for various purposes, as is evidenced, for instance, in 
U.S. Pat. Nos. 959,119, issued May 24, 1910, 2,049,690, issued Aug. 4, 
1936, and 2,870,647, issued Jan. 27, 1959. However, as should appear 
self-evident hereinafter from the following summary and detailed 
description, the arrangement of the present invention utilizes what is 
considered to be an improved Geneva mechanism used in an improved manner 
and further placed in a unique combination with a segmented visor-like 
hood, cover or shutter assembly in a novel way for providing protection to 
an optical window. 
SUMMARY OF THE INVENTION 
The present invention relates to a visor-like hood, cover or shutter 
assembly that may consist of two or more cover or shutter segments pivoted 
about a common pivot or axis and being of progressively increasing radii 
so as to ensure their nested relation to each other when in their open and 
undeployed condition. The outermost segment is driven by a combined motor 
drive means and Geneva mechanism that includes, in part, a prime 
mover-drive motor, a drive shaft, a drive wheel mounted on the drive shaft 
and a driving wheel that is intermittently driven by the drive wheel, as 
will be further explained hereinbelow. The Geneva mechanism, which, in the 
present invention, is considered to be a novel improvement over 
previously-developed Geneva movements as will appear obvious from the 
further description thereof to be set forth hereinafter, comprises, in 
addition to the aforesaid drive and driven wheels, a set of three integral 
cam follower rotatable drive pins or rollers affixed to, and extending 
outwardly of the outer face of the drive wheel, in offset relation to the 
pivot thereof, which drive pins or rollers sequentially engage 
appropriately located radial slots formed in the driven wheel, which 
radial slots are open at the periphery of said driven wheel. 
The aforementioned driven wheel has an integral pinion on its outer face 
that engages with an enlarged gear that is mounted on the inner end of an 
output shaft which, in turn, mounts a drive sprocket on the outer end 
thereof. A drive chain interconnects between the drive sprocket and a 
driven sprocket that is rigidly affixed to the outermost cover or shutter 
segment and is collectively pivotal therewith. With this arrangement, the 
said outermost cover or shutter segment is directly driven or, in other 
words, pivoted about the common pivot point or axis by the operation of 
the drive motor to its closed or deployed position over and in front of 
the optical window intended to be protected thereby. Of course, the 
reverse operation of the said motor returns the outermost cover or shutter 
segment to its open, retracted position. Since the said outermost cover or 
shutter segment is the only one being directly driven by the drive motor 
and the interconnecting drive and drive means, as well as the novel Geneva 
mechanism referred to above, other means consisting of leading and 
trailing overlaps or lips respectively formed on said segments are used 
both to deploy and retract the intermediate and inner segments of the 
plurality of three segments of the instant invention between their opened 
and closed positions, in the manner to be described in detail hereinafter. 
The previously-described drive wheel actually drives the driven wheel 
through a total of 270.degree. in angular rotation in three distinct and 
separate 90.degree. steps, upon the completion of which and as is 
specifically taught by the present invention, a unique dwell period 
occurs. This results from the use of a dwell channel or channeled segment 
incorporated on the outer face of the drive wheel at a selected portion of 
the periphery thereof, which channeled segment respectively engages, in 
successive order, a first pair of oppositely-disposed dwell pins or 
rollers, formed on the inner face of the driven wheel, when the cover or 
shutter segments have been pivoted to their fully extended, deployed 
position. The latter action initiates the dwell period, during which time 
the driven wheel is actually locked in position. At the said dwell period 
initiation, one of a pair of oppositely-disposed cams, utilizable on the 
inner face of the drive wheel in a conventional manner, engages and 
actuates a limit switch which shuts off the electrical power to the drive 
motor, which, coupled with the dynamic, standard braking of the said 
motor, assures the stopping of the further rotation of the drive wheel 
well within an additional 90.degree. of angular rotation, during which 
time the novel dwell period afforded by the unique channeled segment of 
the drive wheel remains effective to thereby prevent damage to the system 
during the measurable time period required to fully stop the operation of 
the drive motor and the rotation of the drive wheel. Of course, the 
opening of the cover or shutter segments to their retracted, nested 
position is effected by reversing the operation of the drive motor. Again, 
the outermost cover or shutter segment is pivoted towards its opened 
position and, by virtue of a droop lip on the forward edge of the said 
outermost segment successively engaging the previously-noted forward edge 
lips on the middle and inner shutter segments, successively picks up and 
carries the said last-named shutter segments to the retracted, completely 
open position. Again, at this moment, two operations simultaneously occur; 
namely, the engagement and actuation of the limit switch by a second cam 
on the inner face of the drive wheel to thereby shut off the electrical 
power to the drive motor, and the initiation of another dwell period 
through the engagement, in consecutive relation, of the uniquely-provided 
drive wheel-mounted, channeled segment with a second pair of 
oppositely-disposed dwell pins or rollers disposed along an axis oriented 
on the driven wheel-inner face in perpendicular relation to the said 
first-named pair of dwell pins or rollers. Thus, protection against damage 
to the system is ensured by the unique dwell period built into the novel 
apparatus of the present invention during the time it takes for the 
complete stoppage of the drive motor, drive shaft and drive wheel after 
the electrical power to the motor has been shut off. 
Other objects and advantages of the present invention will readily appear 
hereinafter in the following disclosure, taken in connection with the 
accompanying drawings, in which:

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring generally to the drawings and, in particular, to FIG. 1, thereof, 
the overall assembly constituting the new and improved optical window 
protective cover or shutter mechanism of the present invention is 
indicated generally at 10 as comprising a visor-like segmented cover or 
shutter device that preferably includes a series of three cover or shutter 
segments 11, 12 and 13, depicted in their closed, extended and optical 
window-protective positions in the aforesaid FIG. 1, in a unique 
combination with a novel cover or shutter control drive mechanism, 
indicated generally at 14 (note, also FIG. 5). Said cover or shutter 
control drive mechanism 14 comprises mover-gearhead, reversible drive 
motor 15 having a drive shaft 16 on which may be affixed the drive wheel 
17 of a Geneva-type mechanism that constitutes a key feature of the 
present invention for the reason that it is improved over conventional 
Geneva movements in a novel and yet simplified manner to appear 
self-evident hereinafter. In addition to drive wheel 17, the present 
Geneva mechanism 14 further includes a star-type, driven wheel 18 that is 
driven in rotation through means of a series of three cam 
follower-rotatable pins or rollers 1, 2 and 3 projecting outwardly from 
the outer face of the drive wheel 17 and which sequentially engage in each 
of a series of four, relatively elongated, radial slots, indicated 
generally at 20, formed in the star-type, driven wheel 18. The specific 
operation of the drive rollers 1, 2, and 3 in the slots 20 will be 
described in more detail hereinafter in specific connection with FIGS. 
6-12, inclusive. 
Again, referring to FIGS. 1 and 5, it is seen that the driven wheel 18 
incorporates an integral, step-down pinion 21 on its outer face that 
engages with an enlarged gear 22 integrally formed on the inner end of an 
output shaft 23 that is shown extending through the optical window-housing 
wall 29 in FIG. 5. To the outer end of the shaft 23 may be attached a 
drive sprocket 24 that is in driving engagement with a driven sprocket 25 
by means of an interconnecting drive chain, at 26. Sprocket 25 may, as is 
depicted, be integrally formed to the pivoted, inner end portion of the 
cover or shutter segment 11 which actually constitutes the outer one of 
the series of three such segments previously described. As is more clearly 
depicted in FIG. 2, for example, the segments 11, 12 and 13 may each 
essentially consist of an equal angle segment of a sphere with appropriate 
varying diameters or, in other words, of progressively decreasing radii, 
and, also, pivotally mounted about a common pivot point or axis at 27 to 
thereby facilitate the concentric or nested stowage thereof when in their 
open or retracted position, as is illustrated in the aforementioned FIG. 
2. 
Referring specifically to the above-mentioned FIG. 2, the optical window 
which the inventively operated three-part cover or shutter mechanism 10 is 
designed to protect when in the closed position is indicated at 28 with 
the previously-noted housing being used for its support denoted at 29. As 
has been previously noted, the outer cover segment 11 is the only directly 
driven element of the set of three. In this regard, after operation of the 
previously-described cover or shutter control drive mechanism has been 
initiated to move the segmented cover or shutter 10 from its open position 
of FIG. 2 to the closed position of FIGS. 3 and 4 in front of, and thereby 
providing protection to the optical window 28, which motor drive operation 
initially effects the direct movement of the outer cover segment 11, as 
noted hereinabove, a lip, as at 11a and 12a, respectively formed on the 
trailing edges of the said outer cover segment 11 and the middle cover 
segment 12 automatically engages a complementary lip, as at 12b and 13b, 
incorporated respectively on the forward edges of the middle and inner 
cover segments 12 and 13. In successive sequence, therefore, first, the 
outer cover segment 11 is pivoted from the retracted, open position of 
FIG. 2 to its closed position (FIGS. 3 and 4) with respect to the optical 
window 28, followed in order by both the middle and inner cover segments 
12 and 13 through the engagement between the aforementioned trailing edge 
lips 11a and 12a with the corresponding forward edge lips 12b and 13b of 
the cover segments 12 and 13 located directly beneath the next preceding 
segment. Of course, inner cover segment 13 is likewise equipped with a 
trailing edge lip at 13a that engages with a stop element 29A (FIG. 3) 
formed on the periphery of the housing 29 for thereby providing a positive 
means of limiting further closing movement of the inventive shutter. With 
this technique, and when the cover or shutter control drive mechanism is 
operated in a reverse manner to reposition the cover segments 11, 12 and 
13 to their open position of FIG. 2, a so-called "droop" lip 11b on the 
forward edge of the outer cover segment 11 sequentially engages and thus 
carries the middle and inner cover segments 12 and 13 to the said 
retracted, open position in nested relation to each other and collectively 
against a second limit stop element at 29b. 
The Geneva mechanism of the instant invention offers, as in the case of 
other such mechanisms, intermittent rotary output motion. In addition, it 
provides, in a unique and yet simplified arrangement, a combined feature 
including the inherent ability of ensuring that, when a drive roller, as 
at 1, 2 or 3, mounted on the drive wheel 17 engages one or the other of 
the radial slots, as at 20 (FIG. 1), formed in the driven, star wheel 18, 
this engagement occurs while the wheel 18 is at rest and therefore the 
impact load therebetween is zero. This characteristic, which will be 
further described in more detail hereinbelow, is already known per se, as 
is evidenced by the teaching in FIG. 3 of U.S. Pat. No. 2,049,690 
previously referred to in the "Background of the Invention". However, the 
driven, star wheel 18 of the present system is improved thereover by 
specifically incorporating additional and novel means, to be further 
described in detail with respect to FIGS. 6-12, for providing a unique 
"dwell period" both on the closing and the opening of the inventive 
segmented cover or shutter mechanism to thus ensure against any damage to 
the apparatus resulting from the continued operation of the cover or 
shutter control drive mechanism 14. 
With particular reference to FIG. 6, the previously-described drive rollers 
1, 2 and 3 are clearly depicted as being respectively mounted in a 
clockwise direction at 90.degree. angles to each other and in each of 
three quadrants of the drive wheel 17, the fourth, drive roller-free 
quadrant incorporating a novel channeled segment 30 to provide the unique 
dwell periods previously referred to hereinabove during both the closing 
and opening of the inventive cover or shutter mechanism. As will be 
explained in the following description, said drive rollers 1, 2, 3 
sequentially engage in the driven wheel-incorporated, radial slots, 
indicated generally at 20, and which are open at the periphery of the 
driven wheel 18 in a conventional manner and as with the drive rollers 1, 
2, and 3, are also oriented at 90.degree. angles to each other. 
These slots have been denoted more specifically at 20a, 20b, 20c and 20d 
reading in a clockwise direction. To initiate the pivotal movement of the 
cover segments 11, 12 and 13 from their open, retracted position of FIG. 2 
to their closed, extended position of FIG. 3, the motor 15 (FIG. 1) is 
actuated to begin the counterclockwise rotation of both the drive shaft 16 
and the drive wheel 17 (note the arrow A in FIG. 6). Upon the said 
counter-clockwise rotation of the drive wheel 17, initially, the first 
drive roller 1, which has been previously positioned so that it is about 
to enter the first radial slot 20a, now actually engages and enters the 
said slot 20a at its open peripheral end while rotating with the drive 
wheel 17 in the aforementioned counterclockwise direction. At this 
instant, the driven wheel 18 is naturally at rest so that its angular 
velocity is zero and, therefore, there is no impact load between the 
driven roller 1 and driven wheel 18. The engagement of the drive 
wheel-roller 1 with the driven wheel - slot 20a causes the driven wheel 18 
to initially accelerate in rotation in a clockwise direction (note arrow 
B) to a maximum velocity through a 90.degree. arc that is commensurate 
with the geometry thereof and then subsequently decelerate to zero 
velocity, stopping further rotation of the driven wheel 18 as the drive 
roller 1 exits from the slot 20a, depicted in FIG. 7. It is noted that 
this feature incorporated in the present apparatus is already known per se 
since it is specifically taught in the previously-referred to FIG. 3 of 
U.S. Pat. No. 2,049,690. As explained in the latter patent, due to the 
straight configuration of the radial slots and the movement of the drive 
rollers, as at 1, along a curved path initially into the slot and then 
away from the slot, as at 20a, the maximum acceleration being imparted to 
the driven wheel 18 increases until the point at which the drive roller 1 
reverses its direction relative to the radial slot from an entering to an 
exiting condition. 
As was previously-described with particular reference to FIG. 1, the 
angular motion or rotation being imparted to the driven wheel 18 is 
transferred by a step-down gear train (also note FIG. 5) first to the 
drive sprocket 24 and then to the driven sprocket 25 through the 
interconnecting, drive chain 26. Driven sprocket 25 is, of course, affixed 
with and thus effects the simultaneous pivoting of the outer cover or 
shutter segment 11 to its closed position relative to the optical window 
28 (FIG. 3). The gear ratio between the pinion 21 (FIG. 1) integral with 
the driven wheel 18 and enlarged gear 22 integral with the output shaft 23 
mounting the drive sprocket 24 is chosen such that the angular movement 
imparted to the driven wheel 18 by roller 1 from the moment it enters the 
slot 20a until departing the said slot causes the outer cover or shutter 
segment 11 to pivot from its open position of FIG. 2 through an 
approximate 45.degree. angle to where the lip 11a (FIG. 3) on its aft end 
or trailing edge will engage the lip 12b on the forward edge of the middle 
cover or shutter segment 12. It is, of course, at this moment that the 
driven wheel 18 has now come to a rest position because of the reverse 
movement and exit of the drive roller 1 from the radial slot 20a, as 
explained hereinabove. Thus, the outer cover - trailing edge lip 11a 
engages the middle cover - forward edge lip 12b in a zero velocity and 
impact-free manner. 
With particular reference to FIG. 7, it is clearly depicted that as roller 
1 exits from the slot 20a, the second drive roller 2 has now reached a 
position where it is entering the next or second slot in the driven wheel 
18; namely, slot 20b. Of course, roller 2 is now entering slot 20b due to 
the previous rotation of the driven wheel 18 by the roller 1 through an 
initial angle of 90.degree.. Once again, the driven wheel 18 is driven by 
the second drive roller 2 through a second 90.degree. angle or now a total 
of 180.degree. from its original orientation, simultaneously causing both 
cover or shutter segments 11 and 12, because of the now-engaged lips 11a 
and 12b, to collectively pivot further into their closed positions in 
front of the optical window 28 (FIG. 3) where the aft end or trailing edge 
lip 12a on the middle segment 12 immediately thereafter engages a forward 
edge lip 13b on the inner cover or shutter segment 13. Again, this 
engagement will occur at zero velocity and no impact forces will result 
therebetween. 
As the above-outlined second drive roller 2 is exiting from the slot 20b in 
the driven wheel 18, as seen in FIG. 8, the third drive roller 3 is 
entering the next or third slot 20c in the driven wheel 18. Again, the 
rotation of the driven wheel 18 by the said third drive roller 3, which is 
now the third 90.degree. increment through which the driven wheel 18 is 
rotated for a grand total of 270.degree., will now effect the simultaneous 
rotation of all three interengaging cover or shutter segments 11, 12 and 
13 to their completely closed and overlapping positions in protective 
relation in front of the optical window 28 as is clearly indicated in the 
aforementioned FIG. 3 (note also FIG. 4). Naturally, the arrival of all 
three cover or shutter segments 11, 12 and 13 in their final, completely 
closed position will once again occur at zero velocity for the same 
reasons previously discussed. 
In partial summary, therefore, the Geneva mechanism 14 provides for 
90.degree. increments of movement of the driven wheel 18. This movement, 
in conjunction with the gearing 21 and 22 and the drive sprocket 24, can 
produce the desired incremental travel of the shutters 11, 12 and 13 in 
approximate 45.degree. increments. It is to be understood, however, that 
the shutters can be pivoted in any desired increment simply by altering 
the gear ratios and/or the ratio of drive sprocket 24 to driven sprocket 
25. 
In accordance with the still further teachings of the present invention, 
after the previously-described cover or shutter segments 11, 12, 13 have 
been fully closed, a unique feature of the inventive Geneva mechanism 
comes into play; namely, the inherent ability to provide a built-in period 
that positively ensures that no output or continued rotation of the driven 
wheel 18 is effected even though the drive wheel 17 continues to rotate 
during the relatively short time period required for shutting down the 
drive motor 15. This period of non-rotation of the driven wheel 18, known 
as the "dwell" period, results from the featuring of a channeled segment, 
seen at 30 in FIGS. 6-12, which channeled segment 30 is uniquely built 
into, or made integral with and projects outwardly of a portion of the 
circumference of the said drive wheel 17 at the remaining quadrant thereof 
not equipped with a drive roller, as at 1, 2 or 3. To bring the said dwell 
period into operation at the appropriate times, the drive wheel 17 is 
further equipped with a series of four rotatable dwell pins or rollers, 
indicated at I, II, III and IV as being integral with, and projecting 
outwardly of the inner face of the said drive wheel 17. Thus, as viewed in 
FIG. 9, initiation of the inventive dwell period is effected by the 
automatic engagement of the said driven wheel - incorporated, channeled 
segment 30 with the first dwell pin, or roller I, just as the third drive 
roller 3 on the said drive wheel 17 is exiting from the driven wheel - 
third slot 20c. Once the said automatic engagement occurs between the said 
channeled segment 30 and dwell roller I, the drive wheel 17 can continue 
to rotate without causing any further movement in rotation of the driven 
wheel 18. In other words, the latter wheel 18, as well as the shutter 
covers 1, 2 and 3, are now locked in their previous adjustment in rotation 
of a total of 270.degree. throughout the dwell period. The said dwell 
period continues from its initiation in FIG. 9 to its maximum extent of 
FIG. 10, or, in other words, until the second dwell roller II, which is 
initially engaged within the channeled segment 30 on the exiting therefrom 
of the first dwell pin I, is cleared by the said channeled segment 30, 
this occurring only after a total 90.degree. rotation dwell period has 
ensued. At this time, the first drive roller 1 on the drive wheel 17 has 
again entered a slot, namely, the fourth slot at 20d in the driven wheel 
18. However, in accordance with the still further teachings of the present 
invention, no effort can now be made to repeat the foregoing sequence of 
operating the above-described segmented cover or shutter mechanism 
comprising segments 11, 12 and 13 which are now in their fully closed 
position in front of the optical window 28 and cannot be physically 
rotated any further. Naturally any continued application of force on the 
drive wheel 18 would cause a build-up of static stresses, eventually 
damaging the bearings and gears. Therefore, at the instant the dwell 
period - creating, channeled segment 30 engages the first dwell roller I, 
one of a pair of oppositely disposed cams (not shown) placed, for example, 
on the inner face of the drive wheel 17 would engage and actuate a limit 
switch 31 (FIG. 1) to turn off the electrical power and stop further 
operation of the motor 15. This, coupled with the conventional dynamic 
braking thereof, would assure that the motor 15 and its drive shaft 16 
would come to a complete stop well within the 90.degree. dwell rotation 
period specifically provided for this novel purpose by the unique 
channeled segment 30. 
To operate the cover or shutter segments 11, 12 and 13 to their open 
position relative to the optical window 28 or, in other words, to initiate 
their retraction into the nested position of FIG. 2, the gearmotor 15 is 
reversed to thus now rotate the drive wheel 17 in the opposite or 
clockwise direction, as in FIG. 11 (see arrow A). The drive wheel 17 will 
then rotate without effecting any movement of the driven wheel 18 until 
the previous dwell period has been retracted. As the channeled segment 30 
of the drive wheel 17 clears dwell roller I on the driven wheel 18, the 
third drive roller 3, as viewed in FIG. 11, on the said drive wheel 17 
begins re-entering the third slot 20c which it had previously departed. 
This action will effect rotation of the said driven wheel 18 in the 
counterclockwise direction (note arrow B), causing cover or shutter 
segment 11 to rotate toward its open position of FIG. 2. As the said drive 
roller 3 reaches its exit position from the slot 20c, again slowing down 
the rotating driven wheel 18 to zero velocity, and the second drive roller 
2 enters the next slot 20b, cover or shutter segment 11 will have rotated 
90.degree. in the open direction until the previously-described 
overhanging or droop lip 11b (FIG. 3) on its forward edge has just come 
into contact with the forward edge or lip 12b of the middle cover or 
shutter segment 12, again, at zero velocity. Said drive roller 2 now 
further rotates the driven wheel 18 a second 90.degree. increment to 
thereby cause the outer and middle cover or shutter segments 11, and 12 to 
similarly rotate an approximate 45.degree. towards their opened positions. 
Thereafter, drive roller 2 exits its slot 20b and drive roller 1 enters 
the next slot 20a and, again, the overhanging or droop lip 11b on the 
forward edge of the outer segment 11 will engage the forward edge or lip 
13b of the inner segment 13 (FIG. 3) at zero velocity as before. 
Simultaneously therewith, drive roller 1 is entering the radial slot 20a 
and causes all three of the cover or shutter segments 11, 12 and 13 to now 
collectively pivot together into the fully open position of FIG. 2. At 
this time, once more, the unique dwell period of the instant invention 
automatically comes into operation with the drive roller 1 exiting the 
slot 20a in the driven wheel 18, whereupon, the channeled segment 30 of 
the driven wheel 17 now begins to engage the driven wheel-mounted, dwell 
roller III and, again, a dwell period is initiated, as has been depicted 
in FIG. 12. Of course, at this instant, the second of the conventional and 
oppositely-disposed pair of cams (not shown) on the inner face of the 
drive wheel 17 has now been rotated to a position of engagement with, and 
operation of the limit switch 31 (FIG. 1) to again shut off the electrical 
power to the motor 15. Of course, as in the case of the opening the cover 
or shutter segments 11, 12, and 13, with the combination of the unique 
channeled segment 30 on the circumference of the drive wheel 17 to thereby 
produce a dwell period for another 90.degree. of rotation, there will be a 
positive assurance that the drive motor 15, when shut off by the 
conventional engagement of the previously-mentioned drive wheel - mounted 
cam with a standard limit switch, as at 31, and the dynamic braking 
thereof in any standard and already-available manner, will have more than 
ample time to completely cease operations before any damage to the 
apparatus can be accomplished. 
Although the foregoing description is had with respect to a segmented 
shutter mechanism specifically designed for use with an optical window 
such as may be used in an infrared air-to-ground weapon delivery system, 
it is to be understood that the invention is obviously of greater utility 
and is limited only by the appended claims.