Method and apparatus for measuring pneumatic differential drag forces

A differential drag apparatus is disclosed for detecting air pressure forces on a drag-sensing body. The body is movable in response to a predetermined magnitude of air pressure force. A pressure regulator responds to the movement of the body by releasing uniform pressure to an activation system. The activation system in turn releases a trigger provided the air pressure force acting against the drag-sensing body remains above the predetermined magnitude for a predetermined length of time. The trigger upon release may perform any number of activates such as opening or closing an electrical circuit, initiating a mechanical response, i.e. releasing a parachute, or detonating a small munition charge. The detonation of a charge, for example, may in turn ignite a rocket motor, release an explosive, or any other of related activities. The apparatus is insensitive to short duration forces above or below the predetermined magnitude, and radiation as results from proximate nuclear blast. The trigger and regulator are initially primed by a pyro-train fuse; yet, activated only by differential movement of the drag-sensing body for a predetermined length of time.

BACKGROUND OF THE INVENTION 
This invention relates to a pneumatic differential drag force detector 
which responds to a predetermined magnitude of force over a sustained 
duration by releasing a signal which in turn activates a specified 
activity. More particularly, this invention relates to a pneumatic 
differential drag force detector which is adaptable to the head of an 
unarmed decoy missile for detecting air pressure forces on re-entry of the 
missile into the earth's atmosphere and for responding to the force of a 
predetermined magnitude for a sustained duration by igniting a rocket 
motor or related activity. 
Various methods have been disclosed in the prior art for detonating a 
firing assembly which would in turn discharge a munition explosive. 
Missiles and related airborne artillery equipment are frequently activated 
directly or indirectly by means of air pressure forces. Ram air pressure 
routed through a conduit system is known for arming a munition. Murphy, 
U.S. Pat. No. 3,841,220, and Rongus, U.S. Pat. No. 3,974,773. Pneumatic or 
fluid pressure has also been used to arm a firing system powered by a 
coiled-spring. Czajkowski et al. U.S. Pat. No. 3,981,329, Hermanson, U.S. 
Pat. No. 4,015,533, and Anderson et al. U.S. Pat. No. 3,962,974. 
In the case of atomic warheads, the missile is often traveling at an 
altitude of 200,000-300,000 feet. The air pressure at this altitude on a 
sensor several inches in diameter, even at very high velocities, is only 
on the order of a few grams. As the missile descends, the air pressure 
increases. At a predetermined point the ignition of a rocket motor or 
related activity is desirable. Therefore, a very sensitive and durable 
drag-sensing body is required to detect small forces above a predetermined 
magnitude and initiate a response due to that detection. At the same time, 
the drag-sensing body must be capable of withstanding proximate nuclear 
blasts--defined as nuclear hardness. The sensor system must filter out 
short duration forces above the predetermined magnitude which will move 
the body. Only a force above the predetermined magnitude which remains for 
a predetermined length of time must activate the system. 
The detonation on the firing assembly via signals from a sensor may 
initiate a number of activities other than discharging an explosive. For 
example, it may activate a relay which controls the ascension or 
descension of a craft. It may also ignite a rocket motor as noted above. 
In Chevrier et al. U.S. Pat. No. 3,992,999, a barometer is used to trigger 
a firing assembly which releases a parachute. It is obvious to those 
skilled in the art that may types of activities may be initiated by 
discharging a firing system. 
It has been a particular problem, however, to develop a sensitive and 
durable sensing device which can remain inoperable for an indefinite 
length of time yet activated on a short time notice with assured 
reliability of performance. The prior art is complicated by a plurality of 
mechanical components which significantly inhibit their ability to remain 
inoperative for extended lengths of time. Achieving an accurate degree of 
sensitivity has also posed a particular problem in the field. As discussed 
above, the force from air pressure is generally on the order of only a few 
grams at the high altitudes traveled by atomic warhead missiles. While it 
is very important that the sensing means correctly monitors the 
environment, it is particularly important that the sensing device be 
inoperative to short duration forces such as proximate atomic blasts which 
may artificially release the trigger in conventional detonators. 
An additional problem in the art has been the availability of an activation 
system responsive to sensing means which operates with a minimum amount of 
mechanical components. Again there is the need for an activation system 
capable of remaining inoperative for an indefinite lengths of time. The 
prior art is complicated by a plurality lock stems, shear pins, O-rings, 
etc. 
There is a need, therefore, for an efficient, accurate, durable and 
reliable sensor and activation system responsive to environmental 
conditions for activation of a firing assembly thereby discharging a 
munition explosive, rocket motor, or related activities. 
The problems enumerated in the foregoing are not intended to be exhaustive 
but rather are among many which tend to impair the effectiveness of the 
prior art at the high altitudes and speed concerned. Other noteworthy 
problems may also exist; however, those presented above should be 
sufficient to demonstrate that the present art available to users of a 
sensing and detonating device has not been altogether satisfactory. 
SUMMARY OF THE INVENTION 
The invention relates to a novel method and apparatus for detecting 
pneumatic differential drag forces resulting from air pressure on a 
drag-sensing body and responding to the movement of the body due to the 
air pressure with a preestablished activity. While the invention will be 
disclosed in terms of detonating a primer which ignites a rocket motor on 
an unarmed decoy missile, it will be obvious that the differential drag 
detector may be installed on any type of moving body to initiate any 
number of activities such as opening or closing an electrical circuit, 
initiating a mechanical or hydraulic operation, i.e. depressing a brake, 
turning a valve, etc. 
The invention comprises a sensor means, a trigger, a pressure regulator, 
and an activation system. The sensor means includes a drag-sensing body 
exposed to a continuous flow of air. The sensor means is connected to the 
pressure regulator. The regulator supplies uniform pressure to the 
activation system from a high pressure source in response to movement of 
the drag-sensing body. The activation system comprises a bellows chamber 
for receiving the uniform pressure from the regulator. A pressure relief 
outlet is attached to the bellows permitting the escape of the uniform 
pressure from the bellows at a predetermined rate. If the drag-sensing 
body is displaced for a predetermined length of time, the rate of uniform 
pressure released into the bellows of the activation system is greater 
than may escape through the pressure relief outlet. This results in the 
expansion of the bellows. An activation piston, mounted within the 
bellows, is displaced with the expansion of the bellows. The trigger, 
hereafter referred to as the firing assembly, includes a spring-biased 
firing piston. Prior to expansion of the bellows, the activation piston 
restrains the firing piston from striking a primer thereby initiating the 
desired activity. With displacement of the activation piston, the firing 
piston is no longer restrained. With respects to the disclosure, the 
activity disclosed is the ignition of a pyro-conduit igniting a rocket 
motor. However, the invention may perform any number of activities as 
noted above. 
Due to the nature of military missiles, the invention must be capable of 
remaining inoperative for extended periods of time. However, the system 
must be primed prior to detonetion. The priming stage serves not only as a 
means to permit the activation but also as a check on the operation of the 
missile after prolonged inactiveness. The priming system engages the 
firing assembly and activates the regulator by means of a pyro-train or 
prima-cord. A pyro-train is well-known within the art as a fast velocity 
firing fuse. It is often constructed of an outer lead sheath housing 
enclosing a plastic explosive. The train has a very high firing rate on 
the order of 1,000 feet per second. A pyro-train is particularly suitable 
to high velocity missiles and related airborne systems due to severe 
environmental conditions during flight. Proximate nuclear blasts can 
easily damage an electrical transmitting system. Whereas, a high velocity 
firing fuse exploding within a protected lead sheath is particularly 
invulnerable to environmental factors. When the pyro-train is looped 
together within an enclosure, the resulting explosion exerts a very high 
pressure which may be used to drive a piston forward if one wall of the 
enclosure is the head of the piston. In the case of the firing assembly, 
an internal hollow shaft which houses the firing piston is advanced 
forward by the explosion of a loop of the pyro-train fuse within the 
assembly compressing a coiled spring which in turn releases a detent 
thereby preventing the shaft from returning to its original released 
position. In this manner, the firing piston is placed under spring 
pressure ready for detonation of the primer restrained only by the 
activation piston. Concurrently, the priming system laterally displaces a 
needle piston mounted within the regulator away from a hermetical seal 
thereby releasing high pneumatic pressure from a source into the 
regulator. High pressure enters the regulator and is confined with a 
regulating chamber, comprised of a bellows. The regulating chamber is 
under compressive force from a coil spring. An equalized or uniform 
pressure condition results between the pneumatic pressure confined within 
the bellows and the coil spring. The needle piston is initially displaced 
from the hermetical seal by an explosion of a pyro-train loop within an 
enclosure of the regulator. 
The sensor means is equipped with a dampening spring which overcomes forces 
below a predetermined magnitude. Whenever a drag force above the 
predetermined magnitude is detected by the drag-sensing body, it is 
displaced relative to the transporting body thereby releasing the uniform 
pressure from the regulator chamber into the bellows of the activation 
system. If the drag force continues for a predetermined length of time, 
the amount of uniform pressure released into the bellows will displace the 
activation piston within the bellows. In this manner, the second detent 
attached to the activation piston releases the firing piston permitting 
the firing pin free access to the primer. 
It is, therefore, a general object of the invention to provide a novel 
method and apparatus for sensing environmental conditions and responding 
to a predetermined magnitude of air pressure force lasting for a 
predetermined length of time by releasing a trigger resulting in the 
performance of a specified activity. 
Examples of the more important features of the invention have been 
summarized rather broadly in order that the description which follows may 
be better understood and in order that the contribution to the art may be 
better appreciated. There are, of course, additional features of 
applicant's invention which may be described hereinafter and which will 
also form the subject of the claims appended hereto.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1, the invention is a pneumatic differential drag 
apparatus which includes a drag-sensing body 4 connected to a transporting 
body 3. The body 4 is a cone shaped element connected in spaced 
relationship to the front of the main body of a missile. As described in 
greater detail below, the drag-sensing body 4 is displaceable relative to 
the transporting body 3. A space is provided for between the bodies 3 and 
4 to permit relative movement. Since the drag-sensing body 4 is supported 
on the front end of the transporting body 3 and acts as a nose cone for 
the missile, the body 3 will sense maximum air-pressure forces during 
flight. Applicant developed the invention for use on an unarmed decoy 
missile in a war-time application to confuse the enemy as to which 
incoming missiles to destroy via a missile-to-missile defense system. 
Applicant recommends the use of fins 7 in the missile's aero-dynamic 
configuration for improved performance in simulating an armed nuclear 
warhead missile. However, the development of the decoy missile system and 
the characteristics coherent in its operation is not a part of this 
invention. The body 4 which is also illustrated with fins 7 need not have 
fins to perform satisfactorly with respect to the entire invention. 
Indeed, the body 4 need not be cone shaped. A bullet shape or flat end 
face would be permissible. In assessing which shape to use, the streamline 
profile of the body must be considered in evaluating its affect on the 
level of sensitivity. A flat end face body will respond to a lower level 
of air pressure than a streamlined geometric body would. However, as 
discussed in greater detail below, an activation system may be adjusted to 
accommodate the different responses of various geometric shapes by 
altering the sizes of various components within the system which control 
response time. As noted above, the application of this invention is not 
limited to differential drag sensing at the head of a missile. The 
invention has application in detecting differential drag forces on any 
type of moving body such as an automobile, airplane, boat, train, or the 
like with the resulting initiation of a specified activity when an air 
pressure force of a predetermined magnitude is detected for a sustained 
period of time. 
Referring to FIG. 2, an apparatus 2 is shown schematically in its entirety. 
The drag-sensing body 4, is connected to a mechanical linkage 8 which in 
turn connects with a rod 11. As noted above, the body 4 is used to measure 
differential movement relative to the transporting body 3. A preloaded 
dampening spring 14 is secured within a housing 13 and restrained by a 
plate 12 which is attached to the rod 11. Rod 11 continues through 
aperture 50 into compartment 52 of a sensor valve 38. The tip 49 of rod 11 
securely seals aperture 51 when in a relaxed position. The mechanical 
linkage 8 is secured to the transporting body 3 by a pin 10. Lateral 
displacement of the body 4 to the right with respect to the transporting 
body 3 displaces the tip 49 of rod 11 to the left thereby allowing 
pressure to escape from a regulator 15 through aperture 51. The dampening 
spring 14 prevents the lateral movement of rod 11 to the left until 
sufficient force is exerted to overcome the spring 14. In this manner, a 
predetermined level of magnitude is established below which the body 4 is 
insensitive to movement. 
Pyro-trains are commonly used in high speed missiles and airborne 
artillery. As noted above electrical engaging systems often fail due to 
the severe environmental factors associated with war time use. A 
pyro-train 19 as shown in FIG. 1 is connected to a pyro-manifold 20 which 
in turn is attached to a pyro-input 21. The pyro-train 19 is looped within 
a firing assembly 18. Pyro-train 19 exits the firing assembly 18 after 
completing the loop within compartment 22 and continues to the pressure 
regulator 15. Pyro-train 19 is again looped within the pressure regulator 
15, as will be described in detail below, and exits the regulator 15 
continuing back to the manifold 20. In this manner, the ignition of both 
pyro-train leads 25 and 26 at manifold 20 is assured to ignite the 
pyro-train loop and, therefore, the explosive loops within the firing 
assembly 18 and pressure regulator 15. If either lead 25 or 26 of 
pyro-train 19 fails to ignite, the circuit will still be complete with the 
ignition of merely one lead. 
As shown in FIG. 3, the pressure regulator 15 equalizes the high pressure 
from a high pressure source 45 and releases a uniform pressure. The 
pressure regulator 15 includes a needle piston 39 and a support tube 39A. 
The needle piston 39 is laterally displacable within the support tube 39A 
and performs a sealing function by preventing the admission of high 
pressure from a conduit 47 into a compartment 16. Pyro-train 19 enters and 
loops around within compartment 41. After forming the loop, pyro-train 19 
exits compartment 41 returning to pyro-manifold 20 thereby creating a 
continuous loop as described above. With the ignition of pyro-train 19 and 
the subsequent explosion of loop 23 within compartment 41, the tube 39A is 
laterally displaced to the left compressing a coil spring 37. The coil 
spring 37 is restrained between a bellows 42 and a lip 39B of tube 39A. 
The needle piston 39 is anchored within the bellows 42. The bellows 42 
does not provide a rigid base for the coil spring 37. When the tube 39A is 
initially displaced by the explosion of loop 23, the spring 37 retracts 
compressing bellows 42. Since the needle piston 39 is anchored within the 
bellows 42, the needle 39 is laterally displaced from a sealing or first 
position to a retraced or second position left of the first position. When 
retracted to the second position, high pressure is permitted to enter the 
compartment 16. In the prototype, the pressure within the high pressure 
source was 2000 psig. The value of the uniform pressure was 90 psig. In 
this manner, a large supply of pressure will provide an extremely long 
supply of uniform pressure. The bellows 42 is secured within regulator 15 
and is in communication with a sensor valve 38 via aperture 51. As noted 
above, however, the rod 11 is held firmly against aperture 51 whenever the 
body 4 is in a relaxed position. The bellows 42 also serves a sealing 
purpose by preventing loss of pneumatic pressure from within bellows 42 
into compartment 40. Before igniting pyro-train 19, the needle piston 39 
is seated in an air-tight manner against a hermetical seal 46. The seal 46 
is connected to a conduit 47 which is in communication with the high 
pressure pneumatic source 45. The seal 46, therefore, is at the input port 
of the high pressure fluid entering the compartment 16. As the needle 
piston 39 is displaced to the left by means of the explosion of the 
pyro-train loop 23 or expansion of coil spring 37, high pneumatic pressure 
is allowed to enter compartment 16. A bellows 17 is adjacent and open to 
compartment 16. Bellows 17 prevents the leakage of the pneumatic pressure 
along the surface of the needle 39. High pressure fluid enters holes 43 of 
the needle piston 39 and moves along the interior of the needle piston 39. 
The pressure exits needle piston 39 via holes 44 into bellows 42. With the 
explosion of loop 23 within compartment 41, the tube 39A forces the spring 
37 and the bellows 42 to the left. High pressure enters compartment 16 and 
travels to bellows 42 which in turn forces spring 37 to the right. In this 
manner, the pressure inside the bellows 42 and the force exerted by the 
spring 37 are equivalent. As the pressure in bellows 42 decreases, spring 
37 compresses bellows 42 thereby moving needle piston 39 to the left and 
allowing more high pressure to enter bellows 42. The pressure within 
bellows 42 will always equal the force exerted by spring 37. Hence, an 
equalizing condition has resulted with the generation of uniform pressure 
within the bellows 42 also referred to as the regulating chamber. The 
explosion of pyro-train loop 23 releases the needle piston 39 from the 
hermetical seal 46. The needle piston 39 is initially hermetically sealed 
such that the compressive force of the spring 37 against the bellows 42 
and the lip 39B in an inactive state is less than the force required to 
break the seal between needle piston 39 and seal 46. An outside force is 
required to initially break the seal as provided by explosive loop 23. A 
hermetical seal is provided to prevent the slow leakage of pressure from 
the source 45 over a long period of time. The missile which houses this 
invention may remain inactive for many years before the source is checked. 
It is important, therefore, to seal the source thoroughly during its 
inactive state. As noted above, a very large value for the high pressure 
supply is used to provide a long supply of uniform pressure once the 
hermetical seat is broken and the invention is activated. 
With respect to FIG. 4, the firing assembly 18 is illustrated with 
activation system 59 mounted atop. Firing assembly 18 comprises an 
exterior housing 27 which supports a hollow sliding shaft 28. The firing 
piston 29 is laterally displacable within shaft 28. Upon detonation, a 
coil spring 35 advances firing piston 29 to the left detonating a stab 
primer 61. 
The coil spring 35 is securely held in place by end wall 30 of the shaft 28 
and wall 31 of the firing piston 29. A firing pin 62 is attached to wall 
31 of firing piston 29. The stab primer 61 is located directly opposite 
the firing pin 62 attached to exterior housing 27. Pyro-conduit 64 is 
connected to the primer 61 and a rocket motor 65. A detent 32 is connected 
to a leaf spring 34 on the exterior surface of the housing 27. The detent 
32 is laterally restrained by aperture 33 of housing 27. Similar to loop 
23 within regulator 15, pyro-train 19 is looped within compartment 22 of 
firing assembly 18. Pyro-train 19 exits compartment 22 and continues on to 
compartment 41 of regulator 15. This section of pyro-train 19 between 
compartment 22 and compartment 41 is redundant and only necessary to 
ignite loop 23 (FIG. 3) if pyro-lead 25 fails to ignite. 
The activation system 59 controls the sensitivity of the invention by 
determining the response time required to release the firing piston 29. A 
bellows housing 58 is mounted atop exterior housing 27. Activation conduit 
53 is connected to the bellows housing 58 and the sensor valve 38. An 
activation piston 55 is located within bellows housing 58 and displaceable 
along axis 56. Flange 57 is mounted to the distal end of the piston 55 
opposite exterior housing 27. Flange 57 is also attached to bellows 58. 
Piston 55 is laterally restrained by a base plate 55A which is attached to 
the exterior housing 27. A bellows 55B is mounted atop base plate 55A and 
prevents leakage of pneumatic pressure along the surface of piston 55. 
Detent 63 is attached to the base of piston 55 and prevents the lateral 
movement of firing piston 29 toward primer 61. An orifice 60 is attached 
to bellows housing 58 and is in communication with a chamber 54. Upon 
ignition of pyro-train 19, loop 24 advances shaft 28 to the left. The 
spring constant of the coiled spring 35 is small enough to allow the 
lateral displacement of the shaft 28. Once wall 30 of shaft 28 has passed 
aperture 33, detent 32 is free to pass through aperture 33 and enter 
compartment 22. In this manner, shaft 28 is prevented from returning to 
its original position. In addition, coil spring 35 is compressed between 
wall 30 which is restrained by detent 32 and wall 31 which is restrained 
by detent 63. Due to the firing velocity of the pyro-train, loops 23 and 
24 ignite almost simultaneously. The priming stage which includes the 
engagement of shaft 28 and the fracture of hermetical seal 46 is 
multi-functional occurring very rapidly. In the prototype, all bellows 
were manufactured of metal for sealing purposes. Metal offers a 
particularly high leak resistance, low temperature sensitivity, long 
storage life and high nuclear radiation hardness. 
In actual operation, the pyro-input 21 ignites all leads exiting from the 
pyro-manifold 20. With the simultaneous ignition of the pyro-leads 25 and 
26, the shaft 28 of firing assembly 18 and the needle piston 39 of 
pressure regulator 15 are primed as discussed above. Coil spring 35 of 
firing assembly 18 is compressed ready for the release of detent 63 from 
firing piston 29. In addition, pressure within the bellows 42 of regulator 
12 is equalized by the compressive force of coil spring 37 within pressure 
regulator 15. Whenever a differential drag force is sensed by the body 4 
sufficient to overcome the compressive spring constant of dampening spring 
14, the rod 11 is displaced from aperture 51 of sensor valve 38. 
Immediately, the equalized pneumatic pressure from bellows 42 escapes into 
compartment 52 of sensor 38. The pressure continues along activation 
conduit 53 into the chamber 54 of bellows housing 58. Orifice 60 allows 
the leakage of pressure from within compartment 54 at a specified rate. 
When a longterm differential force is sensed by body 4, a continuous 
supply of equalized pneumatic pressure is allowed to enter the chamber 54. 
Since the pressure entering from bellows 42 of regulator 15 is greater 
than the permissible rate of escape across the orifice, the pressure 
builds within the chamber 54. In this manner, the piston 55 is displaced. 
With the displacement of piston 55 along axis 56, detent 63 is displaced 
thereby allowing the firing piston 29 free access to the primer 61. As the 
pressure within bellows 42 decreases, spring 37 displacees needle piston 
39 to the left thereby releasing additional pressure from source 45 into 
the compartment 16. The pressure rapidly migrates to the bellows 42 
wherein it exists via aperture 51 into compartment 52 of sensor valve 38. 
By choosing a specific spring constant for dampening spring 14, the 
magnitude of force required to displace body 4 is determinable. Similarly, 
by varying the size of orifice 60 and the chamber 54 and the spring 
constant of spring 37 within regulator 15, the response time requested to 
release the firing piston 29 is determined. The diameter of the orifice 60 
and the dimensions of the chamber 54 dictate the level of pressure 
required to displace piston 55 whereas the force exerted by spring 37 
determines the uniform pressure leaving regulator 15. Applicant 
illustrates the ignition of rocket motor 65; however, pyro-conduit 64 may 
ignite controls which ascend or descend a craft, discharge explosive 
bolts, release "cable cutters", or any number of related activities. 
The location of the firing piston 29 within firing assembly 18 and needle 
piston 39 within pressure regulator 15 is shown in a primed and engaged 
position in FIG. 5. Detent 32 has passed through aperture 33 of housing 27 
and is restraining shaft 28 from returning to its original position. 
Needle piston 39 is displaced to the left thereby breaking the air-tight 
seal between needle piston 39 and seal 46. At this point, high pneumatic 
pressure is entering compartment 16 and passing along the interior of 
needle piston 39 via holes 43 and 44 into equalizing bellows 42. FIG. 6 
illustrates the flow of equalized air pressure from sensor valve 38 into 
bellows housing 58. When the predetermined magnitude of differential drag 
is sensed by body 4, the rod 11 is laterally displaced allowing equalized 
or uniformed air pressure from bellows 42 to migrate through aperture 51 
into compartment 52 of valve sensor 38. Immediately, the pressure enters 
activation conduit 53 and progresses to the chamber 54 of bellows housing 
58. If the rate of air pressure entering the chamber 54 from activation 
conduit 53 exceeds the maximum allowable flow rate across orifice 60, the 
air pressure within the chamber 54 begins to rise. As the pressure rises, 
the force exerted on flange 57 of piston 55 increases. If the air pressure 
force continues for the predetermined time span reaching the predetermined 
pressure level, bellows 58 expands displacing piston 55 along axis 56. 
With the displacement of piston 55, restraining detent 63 is also 
displaced. In this manner, firing piston 29 which restrains spring 35 in 
compression is free to advance forward detonating stab primer 61 with 
firing pin 62. Pyro-conduit 64 is immediately ignited by the detonation of 
primer 61. As illustrated in FIG. 6, pyroconduit 64 ignites rocket motor 
65; however, pyro-conduit 64 may ignite any number of related activities. 
Additionally, a plurality of pyro-conduits 64 may be ignited from 
detonation of primer 61. In this manner, any number of related activities 
may be ignited simultaneously. 
Thus, it is apparent that there has been provided, in accordance with 
applicant's invention, an efficient and reliable method and apparatus for 
detecting differential drag forces and relaying an activation signal which 
results in the performance of a specified activity. The invention, 
therefore, specifically satisfies the objectives and advantages set forth 
above. Although the invention has been defined in conjunction with 
specific forms thereof, it is evident that many alternatives, 
modifications, and variations will be apparent to those skilled in the art 
in light of the foregoing disclosure. Accordingly, it is intended that all 
such alternatives, modifications, and variations which fall within the 
spirit and scope of the invention as defined in the appended claims be 
embraced thereby.